nature of human behavior essay

The Basic Nature of Human Behavior

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The basic nature of human behavior as altruistic and egoistic is unique and has distinct attributes. Equal importance to these behaviors is the understanding of the natural inclinations of human beings. A further analysis on these topics will bring such concepts to light. To begin, altruistic behavior is defined as presenting an impartial and selfless apprehension for the welfare of others or being unselfish. Pollock (2017) declared that “researchers found that when subjects performed altruistic acts, their behavior triggered the pleasure center of the brain, connected with food and sex.

This indicates that moral behaviors are hardwired into humans’ basic impulses” (p. 89). However, these basic impulses may be negative as well as positive. Kivivuori (2007) inserts that “in addition to obedience, the role of altruism as a general human motive should be examined as a driving force behind both trivial and serious forms of proxy crime” (p. 829). This may propose that the offender might feel that he or she is serving or helping others by committing a wrongdoing or misconduct for them.

On the contrary, criminology has perceived altruism as an influence that reduces misconduct. Communities that inspire helping conduct tend to have fewer wrongdoings than that of others. Kivivuori (2007) states that “however, at the micro-level of individual motivation, criminal acts may be motivated by altruistic feelings, so that the crime itself is a sort of gift to a person or a cause” (p.830). In other words, the crime is viewed (by the wrongdoer) as a contribution to the feelings or wellbeing of the individual they are committing the crime for.

On the other hand, egoistic behavior is defined as a belief that separate self-regard is the real purpose of all cognizant action. Pollock (2017) finds that “egoism postulates that what is good for one’s survival and personal happiness is moral” (p. 42). Egoistic individuals hold that we all place our personal desires before others. Egoistic behavior may cause individuals to have an exceedingly overblown opinion or judgement of themselves. In other words, it is a method of self-delusion instead of a specific mode of observing the world. An individual may be egoistic without being egotistic because they are not one in the same. Hand in hand, there are two forms of egoism discussed by Pollock, psychological egoism and enlightened egoism. Psychological egoism is the understanding that individuals are continuously driven by self-regard and self-centeredness. This may even occur in what seems like an act of altruism. Psychological egoism is the decisive motivation of all voluntary acts and is a craving for an individual’s personal well-being. All acts are observed as selfish arrangements regardless of the fact that the egoist willingly points out that individuals generally try to obscure the defining purposes for their acts. This is due to the fact that hiding such motives is another form of self-interest.

Also, enlightened egoism proposes that serving others is an individual’s own interest. Pollock (2017) acknowledges that this “concept appears to be altruistic because it is in one’s long-term best interest to help others in order to receive help in return” (p. 42). Enlightened egoism also claims that it is an individual’s self-regard to aid others and themselves. It is occasionally advocated as a means rather than an end. It pursues the idea that everyone follows their own regard to exploit the universal affluence.

To continue, natural law is known as a build of static ethical values or inclinations viewed as a foundation for all human demeanor. Wolfe (2003) states that “the first and most abstract notion that can be called ‘natural law’ is that human beings are a certain kind of being, and the features of that being should direct our understanding of how human beings should live” (p. 38). Pollock notes four key natural inclinations in his book. Pollock’s (2017) inclinations include “the preservation of one’s own being is a natural inclination and thus is a basic principal of morality, the essence of morality is what conforms to the natural world, sociability, and the pursuit of knowledge or understanding of the universe” (p. 31). These inclinations are not only seen as natural but also morally correct.

To conclude, the basic nature of human behavior may be altruistic or egoistic in character. Each behavior is unique and both have distinct attributes. The natural law and inclinations of human beings, as well as an understanding of these factors, coincide greatly with each behavior. Here is my question to you: “Do you think altruistic behavior actually exists in crime, or is it simply an excuse individuals use in an attempt to be relieved of trouble or of being charged?”

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• v.39(1); 2016 May

Learning, the Sole Explanation of Human Behavior: Review of The Marvelous Learning Animal: What Makes Human Nature Unique

James s. macdonall.

Psychology Department, Fordham University, 441 E. Fordham Road, Bronx, NY 10458 USA

Seemingly everyone is interested in understanding the causes of human behavior. Yet many scientists and the general public embrace causes of behavior that have logical flaws. Attributing behavior to mental events, emotions, personality, or abnormal personality, typically, is committing one of a number of common errors, such as reification, circular reasoning, or nominal fallacies (Schlinger & Poling, 1998 ). An increasingly frequent error is embracing genetic explanations of behavior in the absence of an identified gene. Similarly, explaining behavior in terms of brain structure or function fails to ask what caused that brain structure or function to develop or function in a particular way.

As Arthur Staats ( 2012 ) notes in his valuable book The Marvelous Learning Animal: What Makes Human Nature Unique , unfortunately, such flawed explanations have prospered at the expense explanations based on learning mechanisms. Consequently, many behavior analysts would like to see a book that uses non-technical language to clearly delineate the limitations of explanations based on mind, brain, genes, and personality. Such a book would clearly describe how human behavior (both typical and problematic) can be understood in terms of learning principles, how myriad daily interactions from right after birth make us who we are, how the relevant behavioral research progresses, how interventions are developed based on the research, and how these interventions are subject to research demonstrating their effectiveness. The book would also describe the proper role of genetics and brain structure and function in an understanding of behavior. Perhaps no single volume can do all of these things equally well, The Marvelous Learning Animal is a useful complement to existing works with which behavior analysts may already be familiar (e.g., Schneider, 2012 ; Skinner, 1953 ).

The Great Scientific Error

Attributing causes of behavior to mind, brain, genes, personality, intelligence, abnormal personality, or genetics Staats calls the Great Scientific Error. According to Staats, learning was overlooked as a cause of behavior because early behaviorists did not develop research programs examining learning principles in complex human behavior, behavior occurring outside the laboratory under natural contingencies. Behaviorisms’ total rejection of “personality, intelligence, attitudes, interests or psychological measurement” (p. 33) exacerbated the problem in two ways. First, many in the general population rejected behavioral views because behaviorists rejected these concepts that seemed self-evidently true. Second, behaviorists did not examine the contingencies producing the behaviors subsumed under these labels. Research on reading and language shows the importance of identifying the natural contingencies in development (Hart & Risley, 1995 ; Moerk, 1990 ). Thus, Staats calls for a new learning paradigm that extends from the genetic basis of learning principles through how these learning principles function in complex human behavior. Given the methodological advances in genetics and neuroscience, Skinner, were he alive to see it, may well have agreed with this approach.

The Human Animal

Homo sapiens , according to Staats, are unique in two ways. First, humans have considerable sensitivity to a wide range of stimuli (e.g., light, sound, heat, and tactile). Within each stimulus modality, humans are not the most sensitive (e. g., many birds see better than we do). Some species can sense stimuli that humans do not sense (e.g., honey bees discriminate polarized light). However, we are the only species with very good sensitivity in many modalities. Similarly, we have a diversified motor system. True, other species have as much or more strength or fine control of specific motor systems (e.g., cats can jump further and with greater accuracy than we can jump). But we are the only species that has very good control of a wide variety of motor systems (e. g., facial muscles, hand/finger muscles, and arm and leg muscles).

Second, diverse sensory and motor systems need a brain that not only relays “messages” from sensory receptors to muscle fibers but also integrates the inputs from diverse sensory receptors along with neural results of prior experience producing complex sets of outputs to muscle fibers (what normally is called learning). It is estimated that humans have upwards of 100 billion neurons and on average several thousand synaptic connections for each neuron (Kolb, Gibb, & Robinson, 2001 ). This very large brain, interacting with our diverse sensory and motor systems, is what makes humans unique.

Child Development and the Missing Link

The Marvelous Learning Animal is informed by Staats’ own scholarly career, in which he focused on examining contingencies of naturally occurring behavior. Once Staats identified what he hypothesized were the critical contingencies, he would manipulate them to see if he could speed development and thereby demonstrate their importance. Throughout The Marvelous Learning Animal , Staats divides behavior and its development, for convenience, into three broad areas: emotion-motivation, sensory-motor, and language-cognitive. Despite these labels, the analysis is thoroughly behavioral; there are no hidden behaviors or processes. In all of these domains, Staats argues, maturation is a function of physical growth interacting with natural contingencies, which change as a child’s behavior changes. In Staats’ world view, there is no separate process of child development.

Staats rejects genetics (except for those that program for unconditioned reflexes) and epigenetics as the cause of any behavior. Much of the evidence supporting genetic and epigenetic accounts takes the form of documenting that behavioral disruption results when genetic mechanisms are perturbed. Missing from these accounts, however, is an explanation of how, in relevant disorders, changes in genes affect learning. Thus, the behavior analyst’s task is to identify how a defective gene disrupts learning. In Staats’ view, that knowledge combined with knowledge of the natural contingencies that support normal development allow a complete understanding and effective interventions to minimize or eliminate these so-called genetic or epigenetic disorders.

An example from medicine illustrates the general spirit of this approach and its benefits. Phenylketonuria is a genetic disorder that invariably kills young children with a particular defective gene. Investigators identified the defective gene, but did not stop there. They also found that the non-defective version of the gene produces enzymes necessary for metabolizing phenylalanine, an amino acid toxic to neurons at high doses. A diet with limited phenylalanine, supplemental amino acids, and other nutrients prevents phenylalanine from accumulating and killing young children (Macleod & Ney, 2010 ), even though the genetic defect remains.

Identifying the natural contingencies in development is an exciting research area for behavior analysts. The working hypothesis, of course, is that behavior putatively caused by natural selection can instead be understood by prior experiences. For example, many consider exploratory behaviors of infants to result from genetics, as this quote from Skinner (1948, reprinted 1975 ) might be taken to imply: “No one asks how to motivate a baby. A baby naturally explores everything it can get at….” (p. 144). Staats takes the view that exploratory behaviors, and by implication differences in exploratory behaviors, result from natural reinforcement, that is, changes in the environment produced by exploring as when a baby touches an object it may rattle. If natural selection is not responsible for individual differences in behavior, then it follows that these differences result from differences in learning experiences. This is not to say that there are no intraspecies differences in behavior potential. Humans, for instance, evolved genetic and brain mechanisms that are specific to language, but critically it is early experiences that result in language acquisition and language differences across individuals.

As too few behavior analysts have recognized (e.g., Bijou & Baer, 1961 ; Schlinger, 1995 ), only a detailed examination of early experiences can identify the role of environment in typical development, and by extension in atypical development. In the case of language, research suggests a clear role for early experience in language acquisition. For instance, the more children are exposed to verbal interactions, the greater their language competences’ (Hart & Risley, 1995 ; Moerk, 1990 ). This work has inspired a spate of programs to increase the number of words heard by young children with, or at risk for, language problems, with the goal of nudging language development toward a more normal developmental trajectory (e.g., Suskind & Suskind, 2015 ). It is not yet clear whether these programs adequately reproduce the natural contingencies identified in Moerk ( 1990 ) and Hart & Risley ( 1995 ), but the general approach is consistent with what Staats’ advocates: using natural contingencies as the inspiration for early intervention strategies for children who are falling behind developmental norms.

Crucial Concepts in Human Development

In explaining development, Staats assigns an important role to classical and operant conditioning, but he proposes that complex human behavior is best understood in terms of behavior repertoires and cumulative learning . These two processes, according to Staats, are unique to humans and, when combined with basic learning processes, account for all human behavior.

For Staats, behavior repertoires are complex sets of related stimulus-control relations. He gives the example of a reading repertoire that was built in a dyslexic child via 64,000 trials with a variety of stimulus-control relations involving letters, words, etc. (Staats & Butterfield, 1965 .). Staats identified a large number of these repertoires and their interrelations. Such a reading repertoire, combined with sensory-motor development, can promote a writing repertoire. The reading repertoire may combine with a repertoire for following spoken instructions to allow individuals to follow written instructions, or combined with a sensory-motor repertoire allowing individuals to write instructions. Individual behaviors can be part of several repertoires, and repertoires can be hierarchical, with bigger repertoires comprised, in part, of smaller repertoires. One important goal of behavioral research, in Staats’ view, is to identifying relations among different repertoires and how contingencies influence these repertoires and their interrelations.

Behavior repertoires result in cumulative learning. In mastery of a repertoire, behaviors learned later are acquired more quickly than previously learned behaviors. For example, children learning to print letters late in the alphabet only require one fourth the trials compared to learning to print the letter A . Additionally, mastering one repertoire can make it easier to master a subsequent repertoire. For example, a sound-imitation repertoire combined with suitable prompts produces a word-imitation repertoire that promotes faster language learning. While it may be uncontroversial among behavior analysts to claim that behavior consists of many repertoires and learning one repertoire facilitates learning others, there are few systematic research programs to identify these repertoires, their components, and the contingencies that produce them and establish and maintain their relation to other repertoires.

Staats speculates that cumulative learning influenced human cultural development. Cultural transmission of learning in effect allows one individual’s repertoire to build upon another’s. As one generation masters a repertoire the succeeding generation can master that repertoire faster and is able to expand that repertoire or beginning learning a repertoire new to the group. Staats gives the example of artistic repertoires becoming more sophisticated across generations. Unfortunately, Staats is somewhat vague on the specific mechanisms driving such changes, implying without sufficient explanation that the cumulative learning of a culture’s individual members somehow translates to intergenerational effects (Skinner, 1984 , was similarly vague in his account of cultural selection). Staats also places great emphasis on contingency-shaped behavior in his account of cultural development and, surprisingly, omits any function for rule-governed behavior.

From a behavior analytic perspective, a further limitation of Staats’ account is uncertainty regarding whether behavior repertoires and cumulative learning, as Staats invokes them, qualify as new concepts. By claiming that these phenomena are uniquely human Staats certainly suggests so, but nevertheless behavior analysts will find much that feels familiar in his use of them. For instance, Staats’ analysis of behavioral repertoires and their complex interrelationships brings to mind how reinforcers organize behavior into operants and how the resulting class of responses may not be identical to the class of reinforced responses (Catania, 2013 ). His description of cumulative learning may relate to learning sets (Harlow, 1949 ), pivotal response (Bryson, Koegel, Koegel, Openden, Smith, & Nefdt, 2007 ), and behavior cusps (Rosales-Ruiz & Baer, ( 1997 ), although Staats is silent on these possible connection. In the end, readers will be left to ponder important questions that are suggested by, but not answered in, The Marvelous Learning Animal , not the least of which concerns what sort of research program may be imagined to test Staats’ ideas.

Learning Human Nature

With the preceding as foundational knowledge, Staats addresses specific types of behavior that supposedly are explained by the Great Scientific Error. For example, intelligence tests subsume a variety of repertoires, such as naming, counting, instruction following, and imitating. Differences in intelligence test scores must therefore be interpreted as differences in acquisition of these behavioral repertoires, not differences in an internal entity called intelligence. Staats points out that intelligence test scores predict school performance not because they describe inherent ability but rather because many of the behavior repertoires required for success in school are assessed in intelligence tests. This leads naturally to the proposal for an analysis of the repertoires comprising what we call intelligent behavior, which would include research on the natural contingencies producing these repertoires and, eventually, attempts to foster development by systematically implementing those contingencies.

Behavior analysts will correctly anticipate that Staats proposes that abnormal experiences produce abnormal behaviors. His examples of problematic early childhood behaviors—including tantrums, yelling, hitting, defiance, and so forth—are familiar, as is his suggestion that how caregivers respond to these behaviors influences whether or not they continue and become more severe. These unfortunate natural contingencies produce behavioral repertories that may eventually qualify the individual for a “psychiatric” diagnosis, and once the diagnosis is in place, it elicits sympathy or fear that may only exacerbate caregiver acquiescence to problem behavior. Within the context of autism and a few other disorders, Staats’ recommendation for action is equally familiar. He prescribes clearly identifying the relevant behavior repertoires, analyzing the abnormal contingencies which produce those repertoires and exploring how these repertoires may, through cumulative learning, produce additional problem repertoires. A particular contribution of The Marvelous Learning Animal is to apply the same approach to understanding the development of dyslexia, paranoid schizophrenia, paraphilias, depression, and other problems less frequently addressed by applied behavior analysts. Staats holds steadfastly to his environmental perspective even in cases where biological damage or genetic abnormalities typically are held to cause the disorder (e.g., Down’s syndrome).

Human Evolution and Marvelous Learning

There is much more in Staats’ analysis that is worthy of consideration by behavior analysts, including his assertion that cumulative learning has been an important influence in human natural selection. As Staats notes, those in the field of human evolution are beginning to reach a similar conclusion (Diamond, 1992 ; Gould, 1977 ; Jablonka & Lamb, 2005 ), although Staats’ account is interesting for the emphasis it places on selection for verbal abilities and how verbal abilities influence selection. Critical thinking is required to examine ways in which the account deviates from those of behavior analysts (see Skinner, 1984 , in reinforcement as a mechanism of natural selection) and evolutionary biologists. In the latter case, Staats’ hardest-to-swallow view, namely that natural selection provides all humans with equal learning abilities because variation in learning ability is selected out. This notion is at odds with the widely accepted notion that natural selection is possible only when populations contain variability (Dawkins, 1976 ).

A Human Paradigm

It is refreshing to see an environment-centric alternative to the Great Scientific Error, and behavior analysts will appreciate Staats’ panache in placing learning at the center of all explanations of human behavior. They also will be interested in his conclusion that radical changes are required in the basic science of human behavior and the application of that science to clinical practice. In Staats’ view, the revised science needs to know much more about how learning and biology combine to produce behavior, which implies relying on techniques (e.g., brain imaging technology, genetic assays) to understand the interrelatedness of learning and biology. Many behavior analysts will sympathize with Staats’ proposition that the field of child development needs to be almost entirely restarted, using sophisticated observational methods required to identify the natural contingencies in development. Perhaps less intuitive, and therefore more challenging, to behavior analysts is Staats’ implication that, ultimately, the study of human behavior can only proceed with a proper study of development as he defines it. For example, an infant lies on their stomach pushes up with their arms which raises their head allowing them to see objects hidden behind other objects. If seeing a new view is reinforcing, or seeing objects previously followed by reinforcers is reinforcing, then infants will continue to push up. As they raise their head further above the surface, more items come into view. Eventually the standing infant may lean toward a favored object. They move a foot, preventing themselves from falling, bringing them closer to a reinforcing object. The first proto step has been naturally reinforced. Although, non-behavior analysts have collected data supporting aspects of this analysis, they did not include the functions of behaviors as walking developed (Adolph, Cole, Komati, Garciagurre, Badaly, Lingemanm, Chan, & Sotsky, 2012 ).

A central irony of behavior analysis is that its adherents (beginning with Skinner, e.g., 1953 ) have maintained that complex environmental relations account for the diversity of human behaviors, while their own work carefully analyzed only a limited range of interesting behaviors. The Marvelous Learning Animal challenges behavior analysts (and other readers) to imagine what a behavior science would look like if it thoroughly examined all of those interesting behaviors. In this regard, it matters little if along the way Staats commits a variety of transgressions such as failing to fully explain every concept, possibly playing fast and loose with natural selection, relying on lay terms that carry mentalistic connotations (this is, after all, a popular press book), and occasionally speaking ill of radical behaviorism.

These details should not be allowed to distract from the book’s essential challenge, which is to ask those who would advance environmental experience as the primary engine of behavior development to develop the science that is needed to test and support such an account. Staats delivers an analysis of complex human behavior that is indisputably behavioral and often consistent with a radical behavioral view. Where the analysis diverges from radical behaviorism as it has traditionally been practiced, it most often offers expansion rather than contradiction and thereby provides a stimulating basis for further inquiry.

Acknowledgments

I thank Bob Allen for his helpful comments on an earlier version of this review. All the remaining shortcomings result from my behavior.

Compliance with Ethical Standards

The preparation of this manuscript was not funded by any organization. I have no ethical conflicts in preparing this manuscript.

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The Influence of Nature and Nurture on Human Behavior Research Paper

• To find inspiration for your paper and overcome writer’s block
• As a source of information (ensure proper referencing)
• As a template for you assignment

Introduction

Historical background, debate in support of nature, interaction of nurture and nature, iq and personality debate.

According to (Moore, 2003), the issue of whether nature has more impact than nurture on ways in which human beings behave has been debated upon for quite some time, where each individual is found to support either of the two according to experience or perceptions. Nature concerns itself with the natural internal qualities possessed by human beings. On the other hand, nurture concerns itself with experiences that human beings have acquired from the environment in which they live. The debate involves how these two factors determine the behavioral as well as physical characteristics of human beings and ways in which they vary. The particular roles of nurture and nature are portrayed in various areas and stages of lives of human beings.

The debate on how nurture as well as nature contributes to behavior of human beings can be traced to historical times. From the nineteenth century to early the twentieth century, opinions were found to consider nature as the determinant of human behavior. This was mainly supported by scientific research on the role played by genes that are inherited by offsprings. Another study that supported nature is natural selection that was conducted by Charles Darwin. Galton wrote a book called “hereditary nature” where he argued that, those people who possessed various gifts were found to originate from parents or family backgrounds that had similar kinds of gifts. He supported his arguments by an analysis that he carried on concerning talents and various professions where he concluded that, they were inherited from particular parents who possessed such talents. He also argued that, character traits improve or get worse throughout generations depending on the traits of parents. However, after the First World War, more research was carried out on the issue of the roles of nurture as well as nature. This particular research challenged the views that were in support of nature as the sole determinant of human beings’ behavior and argued that nurture was a major contributing factor to ways in which human beings behaved (Moore, 2003).

According to (Bouchard, 1997), supporters of nurture argue that, the manner in which human beings behave is primarily determined by the environment in which they are brought up. This particular argument has been supported by several studies performed on the various types of temperaments possessed by children. For example, John Watson, an American psychologist performed an experiment on a young boy which showed that, phobia is as a result of classical conditioning. He argued that, if he was to be given some healthy infants, he would apply his own knowledge to equip them with skills of his choice and they would end up in different specializations regardless of their abilities, race, genetic characteristics and talents.

(Steele, 1981), found that the theory of nurture was also supported by Skinner, another psychologist, who performed experiments using pigeons. He took his time to train them on various dancing styles, which they imitated and after some time they could dance as directed. He also trained them on how to play tennis and twist their bodies to make figure eight which they did as well. These experiments made him to be considered as the founder of the science that deals with behavior. From experiments that he carried out on animals, he inferred that it’s possible to condition the behavior of human beings in a similar manner. This inference supported the fact that human behavior is a product of what is learnt through experience acquired in one’s surroundings.

Another study done by scientists, show that human beings acquire their humor through learning. Acquisition of humor is influenced by the type of culture that one grows up in or the kind of family set up that one is brought up in. For example, if one grows up in a family where people are jovial, peaceful and make a lot of jokes, then he/she will grow up a jovial person who is full of humor which will have been learnt from the environment surrounding him. A study of the behavior portrayed by identical twins show that, when brought up in different environments, they acquire very different behavioral traits showing that nurture plays a very big role in determining the type of traits acquired by human beings. (Bridgeman, 2003)

(Maroni, 2000), found that, the color of hair as well as that of eyes is determined by genes. Supporters of the theory of nature also argue that, traits such as aggression, sexual orientation and intelligence are determined by genes. Therefore, various types of genes have been studied so as to show how nature plays its role in determination of behavior. However, these arguments are feared to be used by some people as an excuse for their bad behavior. This is because; some people are found to argue that, since one or both of their parents or someone in their extended family was a criminal, he/she can do nothing to his/her criminal behavior because its inherited. Others argue that, since their parents are divorced, they too cannot escape it because; even if they marry they will have to divorce. This is a negative application of the transfer of genes through inheritance as people tend to stick to negative behavior since their parents had the same. Possession of the gene that makes people to become gay has also been used to explain the role of nature in its determination of behavior. Studies have shown that, genes determine the ways in which various people are oriented sexually. It is argued that, sexual behavior is usually encoded in one’s genes and that, one does not choose whether to become gay or not. Gay individuals are therefore believed to be naturally attracted to people of a similar sex which comes out without their knowledge and cannot be controlled.

However, debate suggests that, both nurture and nature play essential roles in determining the manner in which human beings behave. This is because; some behavior is usually engrained in human beings before birth, while others develop during interaction with their surrounding environment. Therefore, it is agreed that, the way in which genes are related to behavior greatly differs with the way in which causes are related to their consequential effects. This is because; one’s genes may give a probability of a certain behavior but does not guarantee or restrict someone to behave in that particular manner. This gives individuals an opportunity to decide what they want to become, where environment and their effort takes charge (Lindsay, 2000).

It has been found that, there exist minimal instances where behavior can be taken to be entirely caused by nurture or entirely as a result of nature. For example, a study on some “genetic” diseases like Huntington disease show that, there is a high percentage of possession of the gene that causes it as well as the disease which is similar to the percentage that shows a lack of both. However, the lives of those animals that already have this disease entirely depend on the level of care they get. That is, those that get quality animal husbandry live for a longer time than those that are not taken good cared of. Therefore, though nature causes Huntington’s disease, nurture takes control of the length of life that the sick animals will live. On the contrary, some characteristics of human beings are determined by nurture among them being someone’s native language. It is argued that, children have the ability to learn languages of their choice when they are provided with the necessary facilities to enable them learn. This means that, the language spoken by any individual is not in any case determined by genes or inherited but by the environment in which people leave. Therefore, nurture and nature work together in the determination of behavior in human beings.

Another example of their interaction is an experiment that was carried out by Pinker on the religion as well as language spoken by human beings. Results to his experiment showed that, one’s religion, language as well as political party is not determined by genes. However, on acquisition of the specific choices, characteristics that show temperaments and skills in the form of how well one can communicate in a certain language, how one behaves in his /her political party or the level of commitment to a certain religion are to some extent determined by one’s inherited genes (Lindsay, 2000).

Therefore, when characteristics of human beings’ behavior are caused by interactions of nurture and nature, the level of heritability can only be measured through variations that exist in a given population. But there are cases where scientists have been noticed to assume that, if a particular level of heritability is noticed in a certain trait, that trait has been purely determined by nature, not taking into account the possibility of nurture been involved in some way. However, this should not be case as both determinants play roles in determination of the traits acquired by human beings though their levels of association or involvement vary in different traits (Stuart, 1999).

This debate has attracted a wide range of arguments and suggestions where studies of twins who are identical and fraternal are used. Adopted children are also used for comparison purposes. Studies that support the role played by nature in determination human beings’ IQ argue that, the IQ of those twins who are identical has a high level of similarity even when the two are reared separately. Those supporting nature say that the high level of similarity is caused by their shared genes from the environment they were inside their mothers’ womb. Further studies show that, similarity of IQ diminishes as one moves from twins, to fraternal, to adopted children and finally to strangers. On the contrary, studies supporting nurture argue something different altogether. For example, James Flynn, a political scientist noticed that, the level of human beings’ IQ was accelerating with time. His arguments suggested that, the level of IQ is determined by environmental factors that children are exposed to as they grow up. These environmental factors include, diet, education and the level of IQ of those people with whom children interact with.

Flynn argued that, the complexity of visual images that people are exposed to through advertisements, computer games and posters increase their levels of IQ. Other environmental aspects that tend to affect IQ levels include infant malnutrition where those children who suffer malnutrition possess low levels of IQ as they lack enough energy to reason as well as other nutrients required in reasoning. The profession of parents also matters as it tends to motivate the child in one way or another if it happens to be good. Consequently, studies show that most children tend to follow the professions of their parents as children are likely to imitate their parents. This trend makes the IQ of those children to be determined by the profession and not genes acquired from parents. Another factor that may affect children’s level of IQ is the parental ambition as well as rigidity. A child whose parents are ambitious is likely to be exposed to issues that would in one way or another increase his/her IQ while rigid parents are likely to cause rigidity in their children resulting to lowering their IQ levels (Stuart, 1999).

The manner in which people behave is caused or determined by both nurture and nature. However, involvement of each of them varies depending on the kind of trait in question. Scientists have contributed to this particular debate by performing studies that are directed at differentiating roles played by nature and those played by nurture. Though it is not possible to give an exact estimation of their involvement, it can be concluded that, genes only determine one’s behavior up to a certain age where environment in which he/she is brought up takes over. (Becker, 2002)

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• Pain Management Through Psychology
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• Nature v/s Nurture in Human behaviour development
• The Nocebo Effect: Term Definition
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• Does Dark Weather Bring Dark Moods?
• Emotional Intelligence: Term Definition
• Various Psychologists' Relation to Socialization
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Nature and nurture as an enduring tension in the history of psychology.

• Hunter Honeycutt Hunter Honeycutt Bridgewater College, Department of Psychology
• https://doi.org/10.1093/acrefore/9780190236557.013.518
• Published online: 30 September 2019

Nature–nurture is a dichotomous way of thinking about the origins of human (and animal) behavior and development, where “nature” refers to native, inborn, causal factors that function independently of, or prior to, the experiences (“nurture”) of the organism. In psychology during the 19th century, nature-nurture debates were voiced in the language of instinct versus learning. In the first decades of the 20th century, it was widely assumed that that humans and animals entered the world with a fixed set of inborn instincts. But in the 1920s and again in the 1950s, the validity of instinct as a scientific construct was challenged on conceptual and empirical grounds. As a result, most psychologists abandoned using the term instinct but they did not abandon the validity of distinguishing between nature versus nurture. In place of instinct, many psychologists made a semantic shift to using terms like innate knowledge, biological maturation, and/or hereditary/genetic effects on development, all of which extend well into the 21st century. Still, for some psychologists, the earlier critiques of the instinct concept remain just as relevant to these more modern usages.

The tension in nature-nurture debates is commonly eased by claiming that explanations of behavior must involve reference to both nature-based and nurture-based causes. However, for some psychologists there is a growing pressure to see the nature–nurture dichotomy as oversimplifying the development of behavior patterns. The division is seen as both arbitrary and counterproductive. Rather than treat nature and nurture as separable causal factors operating on development, they treat nature-nurture as a distinction between product (nature) versus process (nurture). Thus there has been a longstanding tension about how to define, separate, and balance the effects of nature and nurture.

• nature–nurture
• development
• nativism–empiricism
• innate–learned
• behavioral genetics
• epigenetics

Nature and Nurture in Development

The oldest and most persistent ways to frame explanations about the behavioral and mental development of individuals is to distinguish between two separate sources of developmental causation: (a) intrinsic, preformed, or predetermined causes (“nature”) versus (b) extrinsic, experiential, or environmental causes (“nurture”). Inputs from these two sources are thought to add their own contribution to development (see Figure 1 ).

Figure 1. The traditional view of nature and nurture as separate causes of development. In the traditional view, nature and nurture are treated as independent causal influences that combine during development to generate outcomes. Note that, during development, the effects of nature and nurture (shown in horizontal crossing lines) remain independent so that their effects on outcomes are theoretically separable.

Because some traits seem to derive more from one source than the other, much of the tension associated with the nature–nurture division deals with disagreements about how to balance the roles of nature and nurture in the development of a trait.

Evidence of Nature in Development

Evidence to support the nature–nurture division usually derives from patterns of behavior that suggest a limited role of environmental causation, thus implying some effect of nature by default. Table 1 depicts some common descriptors and conditions used to infer that some preference, knowledge, or skill is nature based.

Table 1. Common Descriptors and Associated Conditions for Inferring the Effects of Nature on Development

It is important to reiterate that nature-based causation (e.g., genetic determination) is inferred from these observations. Such inferences can generate tension because each of the observations listed here can be explained by nurture-based (environmental) factors. Confusion can also arise when evidence of one descriptor (e.g., being hereditary) is erroneously used to justify a different usage (e.g., that the trait is unlearned).

The Origins of Nature Versus Nurture

For much of recorded history, the distinction between nature and nurture was a temporal divide between what a person is innately endowed with at birth, prior to experience (nature), and what happens thereafter (nurture). It was not until the 19th century that the temporal division was transformed into a material division of causal influences (Keller, 2010 ). New views about heredity and Darwinian evolution justified distinguishing between native traits and genetic causes from acquired traits and environmental causes. More so than before, the terms nature and nurture were often juxtaposed in an opposition famously described by Sir Francis Galton ( 1869 ) as that between “nature versus nurture.”

Galton began writing about heredity in the mid-1860s. He believed we would discover laws governing the transmission of mental as well as physical qualities. Galton’s take on mental heredity, however, was forged by his desire to improve the human race in a science he would later call “eugenics.” In the mid- 19th century , British liberals assumed humans were equivalent at birth. Their social reform efforts were geared to enhancing educational opportunities and improving living conditions. Galton, a political conservative, opposed the notion of natural equality, arguing instead that people were inherently different at birth (Cowan, 2016 ), and that these inherited mental and behavioral inequalities were transmitted through lineages like physical qualities. Because Galton opposed the widely held Lamarckian idea that the qualities acquired in one’s lifetime could modify the inherited potential of subsequent generations, he believed long-lasting improvement of the human stock would only come by controlling breeding practices.

To explain the biological mechanisms of inheritance, Galton joined a growing trend in the 1870s to understand inheritance as involving the transmission of (hypothetical) determinative, germinal substances across generations. Foreshadowing a view that would later become scientific orthodoxy, Galton believed these germinal substances to be uninfluenced by the experiences of the organism. His theory of inheritance, however, was speculative. Realizing he was not equipped to fully explicate his theory of biological inheritance, Galton abandoned this line of inquiry by the end of that decade and refocused his efforts on identifying statistical laws of heredity of individual differences (Renwick, 2011 ).

Historians generally agree that Galton was the first to treat nature (as heredity) and nurture (everything else) as separate causal forces (Keller, 2010 ), but the schism gained biological legitimacy through the work of the German cytologist Auguste Weismann in the 1880s. Whereas Galton’s theory was motivated by his political agenda, Weismann was motivated by a scientific, theoretical agenda. Namely, Weismann opposed Lamarckian inheritance and promoted a view of evolution driven almost entirely by natural selection.

Drawing upon contemporary cytological and embryological research, Weismann made the case that the determinative substances found in the germ cells of plants and animals (called the “germ-plasm”) that are transmitted across generations were physically sequestered very early in embryogenesis and remained buffered from the other cells of the body (“somato-plasm”). This so-called, Weismann’s barrier meant that alterations in the soma that develop in the lifetime of the organism through the use or disuse of body parts would not affect the germinal substances transmitted during reproduction (see Winther, 2001 , for review). On this view, Lamarckian-style inheritance of acquired characteristics was not biologically possible.

Galton and Weismann’s influence on the life sciences cannot be overstated. Their work convinced many to draw unusually sharp distinctions between the inherited (nature) and the acquired (nurture). Although their theories were met with much resistance and generated significant tension in the life sciences from cytology to psychology, their efforts helped stage a new epistemic space through which to appreciate Mendel’s soon to be rediscovered breeding studies and usher in genetics (Muller-Wille & Rheinberger, 2012 ).

Ever since, psychology has teetered between nature-biased and nurture-biased positions. With the rise of genetics, the wedge between nature–nurture was deepened in the early to mid- 20th century , creating fields of study that focused exclusively on the effects of either nature or nurture.

The “Middle Ground” Perspective on Nature–Nurture

Twenty-first-century psychology textbooks often state that the nature–nurture debates have been resolved, and the tension relaxed, because we have moved on from emphasizing nature or nurture to appreciating that development necessarily involves both nature and nurture. In this middle-ground position, one asks how nature and nurture interact. For example, how do biological (or genetic) predispositions for behaviors or innate knowledge bias early learning experiences? Or how might environmental factors influence the biologically determined (maturational) unfolding of bodily form and behaviors?

Rejection of the Nature–Nurture Divide

For some, the “middle-ground” resolution is as problematic as “either/or” views and does not resolve a deeper source of tension inherent in the dichotomy. On this view, the nature–nurture divide is neither a legitimate nor a constructive way of thinking about development. Instead, developmental analysis reveals that the terms commonly associated with nature (e.g., innate, genetic, hereditary, or instinctual) and nurture (environmental or learned) are so entwined and confounded (and often arbitrary) that their independent effects cannot be meaningfully discussed. The nature–nurture division oversimplifies developmental processes, takes too much for granted, and ultimately hinders scientific progress. Thus not only is there a lingering tension about how to balance the effects of nature and nurture in the middle-ground view, but there is also a growing tension to move beyond the dichotomous nature–nurture framework.

Nativism in Behavior: Instincts

Definitions of instinct can vary tremendously, but many contrast (a) instinct with reason (or intellect, thought, will), which is related to but separable from contrasting (b) instinct with learning (or experience or habit).

Instinct in the Age of Enlightenment

Early usages of the instinct concept, following Aristotle, treated instinct as a mental, estimative faculty ( vis aestimativa or aestimativa naturalis ) in humans and animals that allowed for the judgments of objects in the world (e.g., seeing a predator) to be deemed beneficial or harmful in a way that transcends immediate sensory experience but does not involve the use of reason (Diamond, 1971 ). In many of the early usages, the “natural instinct” of animals even included subrational forms of learning.

The modern usage of instincts as unlearned behaviors took shape in the 17th century . By that point it was widely believed that nature or God had implanted in animals and humans innate behaviors and predispositions (“instincts”) to promote the survival of the individual and the propagation of the species. Disagreements arose as to whether instincts derived from innate mental images or were mindlessly and mechanically (physiologically) generated from innately specified bodily organization (Richards, 1987 ).

Anti-Instinct Movement in the Age of Enlightenment

Challenges to the instinct concept can be found in the 16th century (see Diamond, 1971 ), but they were most fully developed by empiricist philosophers of the French Sensationalist tradition in the 18th century (Richards, 1987 ). Sensationalists asserted that animals behaved rationally and all of the so-called instincts displayed by animals could be seen as intelligently acquired habits.

For Sensationalists, instincts, as traditionally understood, did not exist. Species-specificity in behavior patterns could be explained by commonalities in physiological organization, needs, and environmental conditions. Even those instinctual behaviors seen at birth (e.g., that newly hatched chicks peck and eat grain) might eventually be explained by the animal’s prenatal experiences. Erasmus Darwin ( 1731–1802 ), for example, speculated that the movements and swallowing experiences in ovo could account for the pecking and eating of grain by young chicks. The anti-instinct sentiment was clearly expressed by the Sensationalist Jean Antoine Guer ( 1713–1764 ), who warned that instinct was an “infantile idea” that could only be held by those who are ignorant of philosophy, that traditional appeals to instincts in animals not only explained nothing but served to hinder scientific explanations, and that nothing could be more superficial than to explain behavior than appealing to so-called instincts (Richards, 1987 ).

The traditional instinct concept survived. For most people, the complex, adaptive, species-specific behaviors displayed by naïve animals (e.g., caterpillars building cocoons; infant suckling behaviors) appeared to be predetermined and unlearned. Arguably as important, however, was the resistance to the theological implications of Sensationalist philosophy.

One of the strongest reactions to Sensationalism was put forward in Germany by Herman Samuel Reimarus ( 1694–1768 ). As a natural theologian, Reimarus, sought evidence of a God in the natural world, and the species-specific, complex, and adaptive instincts of animals seemed to stand as the best evidence of God’s work. More so than any other, Reimarus extensively catalogued instincts in humans and animals. Rather than treat instincts as behaviors, he defined instincts as natural impulses (inner drives) to act that were expressed perfectly, without reflection or practice, and served adaptive goals (Richards, 1987 ). He even proposed instincts for learning, a proposal that would resurface in the mid- 20th century , as would his drive theory of instinct (Jaynes & Woodward, 1974 ).

Partly as a result of Reimarus’ efforts, the instinct concept survived going into the 19th century . But many issues surrounding the instinct concept were left unsettled. How do instincts differ from reflexive behaviors? What role does learning play in the expression of instincts, if any? Do humans have more or fewer instincts than animals? These questions would persist well into the first decades of the 20th century and ultimately fuel another anti-instinct movement.

Instinct in the 19th Century

In the 19th century , the tension about the nature and nurture of instincts in the lifetime of animals led to debates about the nature and nurture of instincts across generations . These debates dealt with whether instincts should be viewed as “inherited habits” from previous generations or whether they result from the natural selection. Debating the relative roles of neo-Lamarckian use-inheritance versus neo-Darwinian natural selection in the transmutation of species became a significant source of tension in the latter half of the 19th century . Although the neo-Lamarckian notion of instincts as being inherited habits was rejected in the 20th century , it has resurged in recent years (e.g., see Robinson & Barron, 2017 ).

Darwinian evolutionary theory required drawing distinctions between native and acquired behaviors, and, perhaps more so than before, behaviors were categorized along a continuum from the purely instinctive (unlearned), to the partially instinctive (requiring some learning), to the purely learned. Still, it was widely assumed that a purely instinctive response would be modified by experience after its first occurrence. As a result, instinct and habit were very much entangled in the lifetime of the organism. The notion of instincts as fixed and unmodifiable would not be widely advanced until after the rise of Weismann’s germ-plasm theory in the late 19thcentury .

Given their importance in evolutionary theory, there was greater interest in more objectively identifying pure instincts beyond anecdotal reports. Some of the most compelling evidence was reported by Douglas Spalding ( 1844–1877 ) in the early 1870s (see Gray, 1967 ). Spalding documented numerous instances of how naïve animals showed coordinated, seemingly adaptive responses (e.g., hiding) to objects (e.g., sight of predators) upon their first encounter, and he helped pioneer the use of the deprivation experiment to identify instinctive behaviors. This technique involved selectively depriving young animals of seemingly critical learning experiences or sensory stimulation. Should animals display some species-typical action following deprivation, then, presumably, the behavior could be labeled as unlearned or innate. In all, these studies seemed to show that animals displayed numerous adaptive responses at the very start, prior to any relevant experience. In a variety of ways, Spalding’s work anticipated 20th-century studies of innate behavior. Not only would the deprivation experiment be used as the primary means of detecting native tendencies by European zoologists and ethologists, but Spalding also showed evidence of what would later be called imprinting, critical period effects and evidence of behavioral maturation.

Reports of pure instinct did not go unchallenged. Lloyd Morgan ( 1896 ) questioned the accuracy of these reports in his own experimental work with young animals. In some cases, he failed to replicate the results and in other cases he found that instinctive behaviors were not as finely tuned to objects in the environment as had been claimed. Morgan’s research pointed to taking greater precision in identifying learned and instinctive components of behavior, but, like most at the turn of the 20th century , he did not question that animal behavior involved both learned and instinctive elements.

A focus on instinctive behaviors intensified in the 1890s as Weismann’s germ-plasm theory grew in popularity. More so than before, a sharp distinction was drawn between native and acquired characteristics, including behavior (Johnston, 1995 ). Although some psychologists continued to maintain neo-Lamarckian notions, most German (Burnham, 1972 ) and American (Cravens & Burnham, 1971 ) psychologists were quick to adopt Weismann’s theory. They envisioned a new natural science of psychology that would experimentally identify the germinally determined, invariable set of native psychological traits in species and their underlying physiological (neural) basis. However, whereas English-speaking psychologists tended to focus on how this view impacted our understanding of social institutions and its social implications, German psychologists were more interested in the longstanding philosophical implications of Weismann’s doctrine as it related to the differences (if any) between man and beast (Burnham, 1972 ).

Some anthropologists and sociologists, however, interpreted Weismann’s theory quite differently and used it elevate sociology as its own scientific discipline. In the 1890s, the French sociologist Emil Durkheim, for example, interpreted Weismann’s germinal determinants as a generic force on human behavior that influenced the development of general predispositions that are molded by the circumstances of life (Meloni, 2016 ). American anthropologists reached similar conclusions in the early 20th century (Cravens & Burnham, 1971 ). Because Weismann’s theory divorced biological inheritance from social inheritance, and because heredity was treated as a generic force, sociologists felt free to study social (eventually, “cultural”) phenomena without reference to biological or psychological concerns.

Anti-Instinct Movement in the 1920s

Despite their differences, in the first two decades of the 20th century both psychologists and sociologists generally assumed that humans and animals had some native tendencies or instincts. Concerns were even voiced that instinct had not received enough attention in psychology. Disagreements about instincts continued to focus on (the now centuries old debates of) how to conceptualize them. Were they complex reflexes, impulses, or motives to act, or should instinct be a mental faculty (like intuition), separate from reasoning and reflex (Herrnstein, 1972 )?

In America, the instinct concept came under fire following a brief paper in 1919 by Knight Dunlap titled “Are There Any Instincts?” His primary concern dealt with teleological definitions of instincts in which an instinct referred to all the activities involved in obtaining some end-state (e.g., instincts of crying, playing, feeding, reproduction, war, curiosity, or pugnacity). Defined in this way, human instincts were simply labels for human activities, but how these activities were defined was arbitrarily imposed by the researchers. Is feeding, for instance, an instinct, or is it composed of more basic instincts (like chewing and swallowing)? The arbitrariness of classifying human behavior had led to tremendous inconsistencies and confusion among psychologists.

Not all of the challenges to instinct dealt with its teleological usage. Some of the strongest criticisms were voiced by Zing-Yang Kuo throughout the 1920s. Kuo was a Chinese animal psychologist who studied under Charles Tolman at the University of California, Berkeley. Although Kuo’s attacks on instinct changed throughout the 1920s (see Honeycutt, 2011 ), he ultimately argued that all behaviors develop in experience-dependent ways and that appeals to instinct were statements of ignorance about how behaviors develop. Like Dunlap, he warned that instincts were labels with no explanatory value. To illustrate, after returning to China, he showed how the so-called rodent-killing instinct in cats often cited by instinct theorists is not found in kittens that are reared with rodents (Kuo, 1930 ). These kittens, instead, became attached to the rodents, and they resisted attempts to train rodent-killing. Echoing the point made by Guer, Kuo claimed that appeals to instinct served to stunt scientific inquiry into the developmental origins of behavior.

But Kuo did not just challenge the instinct concept. He also argued against labeling behaviors as “learned.” After all, whether an animal “learns” depends on the surrounding environmental conditions, the physiological and developmental status of the animal, and, especially, the developmental (or experiential) history of that animal. Understanding learning also required developmental analysis. Thus Kuo targeted the basic distinction between nature and nurture, and he was not alone in doing so (e.g., see Carmichael, 1925 ), but his call to reject it did not spread to mainstream American psychologists.

By the 1930s, the term instinct had fallen into disrepute in psychology, but experimental psychologists (including behaviorists) remained committed to a separation of native from acquired traits. If anything, the dividing line between native and acquired behaviors became more sharply drawn than before (Logan & Johnston, 2007 ). For some psychologists, instinct was simply rebranded in the less contentious (but still problematic) language of biological drives or motives (Herrnstein, 1972 ). Many other psychologists simply turned to describing native traits as due to “maturation” and/or “heredity” rather than “instinct.”

Fixed Action Patterns

The hereditarian instinct concept received a reboot in Europe in the 1930s with the rise of ethology led by Konrad Lorenz, Niko Tinbergen, and others. Just as animals inherit organs that perform specific functions, ethologists believed animals inherit behaviors that evolved to serve adaptive functions as well. Instincts were described as unlearned (inherited), blind, stereotyped, adaptive, fixed action patterns, impervious to change that are initiated (released) by specific stimuli in the environment.

Ethologists in 1930s and 1940s were united under the banner of innateness. They were increasingly critical of the trend by American psychologists (i.e., behaviorists) to focus on studying on how a limited number of domesticated species (e.g., white rat) responded to training in artificial settings (Burkhardt, 2005 ). Ethologists instead began with rich descriptions of animal behavior in more natural environments along with detailed analyses of the stimulus conditions that released the fixed action patterns. To test whether behavioral components were innate, ethologists relied primarily on the deprivation experiment popularized by Spalding in the 19th century . Using these methods (and others), ethologists identified numerous fascinating examples of instinctive behaviors, which captured mainstream attention.

In the early 1950s, shortly after ethology had gained professional status (Burkhardt, 2005 ), a series of challenges regarding instinct and innateness were put forth by a small cadre of North American behavioral scientists (e.g., T. C. Schneirla, Donald Hebb, Frank Beach). Arguably the most influential critique was voiced by comparative psychologist Daniel Lehrman ( 1953 ), who presented a detailed and damning critique of deprivation experiments on empirical and logical grounds. Lehrman explained that deprivation experiments isolate the animal from some but not all experiences. Thus deprivation experiments simply change what an animal experiences rather than eliminating experience altogether, and so they cannot possibly determine whether a behavior is innate (independent of experience). Instead, these experiments show what environmental conditions do not matter in the development of a behavior but do not speak to what conditions do matter .

Lehrman went on to argue that the whole endeavor to identify instinctive or innate behavior was misguided from the start. All behavior, according to Lehrman, develops from a history of interactions between an organism and its environment. If a behavior is found to develop in the absence of certain experiences, the researcher should not stop and label it as innate. Rather, research should continue to identify the conditions under which the behavior comes about. In line with Kuo, Lehrman repeated the warning that to label something as instinctive (or inherited or maturational) is a statement of ignorance about how that behavior develops and does more to stunt than promote research.

Lehrman’s critique created significant turmoil among ethologists. As a result, ethologists took greater care in using the term innate , and it led to new attempts to synthesize or re-envision learning and instinct .

Some of these attempts focused on an increased role for learning and experience in the ontogeny of species-typical behaviors. These efforts spawned significant cross-talk between ethologists and comparative psychologists to more thoroughly investigate behavioral development under natural conditions. Traditional appeals to instinct and learning (as classical and operant conditioning) were both found to be inadequate for explaining animal behavior. In their stead, these researchers focused more closely on how anatomical, physiological, experiential, and environmental conditions influenced the development of species-typical behaviors.

Tinbergen ( 1963 ) was among those ethologists who urged for greater developmental analysis of species-typical behaviors, and he included it as one of his four problems in the biological study of organisms, along with causation (mechanism), survival value (function), and evolution. Of these four problems, Tinbergen believed ethologists were especially well suited to study survival value, which he felt had been seriously neglected (Burkhardt, 2005 ).

The questions of survival value coupled with models of population genetics would gain significant momentum in the 1960s and 1970s in England and the United States with the rise of behavioral ecology and sociobiology (Griffiths, 2008 ). But because these new fields seemed to promote some kind of genetic determinism in behavioral development, they were met with much resistance and reignited a new round of nature–nurture debates in the 1970s (see Segerstrale, 2000 ).

However, not all ethologists abandoned the instinct concept. Lorenz, in particular, continued to defend the division between nature and nurture. Rather than speaking of native and acquired behaviors, Lorenz later spoke of two different sources of information for behavior (innate/genetic vs. acquired/environmental), which was more a subtle shift in language than it was an actual change in theory, as Lehrman later pointed out.

Some ethologists followed Lorenz’s lead and continued to maintain more of a traditional delineation between instinct and learning. Their alternative synthesis viewed learning as instinctive (Gould & Marler, 1987 ). They proposed that animals have evolved domain-specific “instincts to learn” that result from the its genetic predispositions and innate knowledge. To support the idea of instincts for learning, ethologists pointed to traditional ethological findings (on imprinting and birdsong learning), but they also drew from the growing body of work in experimental psychology that seemed to indicate certain types of biological effects on learning.

Biological Constraints and Preparedness

While ethology was spreading in Europe in the 1930s–1950s, behaviorism reigned in the United States. Just as ethologists were confronted with including a greater role of nurture in their studies, behaviorists were challenged to consider a greater role of nature.

Behaviorists assumed there to be some behavioral innateness (e.g., fixed action patterns, unconditioned reflexes, primary reinforcers and drives). But because behaviorists focused on learning, they tended to study animals in laboratory settings using biologically (or ecologically) irrelevant stimuli and responses to minimize any role of instinct (Johnston, 1981 ). It was widely assumed that these studies would identify general laws of learning that applied to all species regardless of the specific cues, reinforcers, and responses involved.

Challenges to the generality assumption began to accumulate in the 1960s. Some studies pointed to failures that occurred during conditioning procedures. Breland and Breland ( 1961 ), for example, reported that some complex behaviors formed through operant conditioning would eventually become “displaced” by conditioned fixed action patterns in a phenomenon they called “instinctive drift.” Studies of taste-aversion learning (e.g., Garcia & Koelling, 1966 ) also reported the failure of rats to associate certain events (e.g., flavors with shock or audiovisual stimuli with toxicosis).

Other studies were pointing to enhanced learning. In particular, it was found that rats could form strong conditioned taste aversions after only a single pairing between a novel flavor and illness. (This rapid “one trial learning” was a major focus in the research from Niko Tinbergen’s ethological laboratory.) Animals, it seemed, had evolved innate predispositions to form (or not form) certain associations.

In humans, studies of biological constraints on learning were mostly limited to fear conditioning. Evidence indicated that humans conditioned differently to (biologically or evolutionarily) fear-relevant stimuli like pictures of spiders or snakes than to fear-irrelevant stimuli like pictures of mushrooms or flowers (Ohman, Fredrikson, Hugdahl, & Rimmö, 1976 ).

These findings and others were treated as a major problem in learning theory and led to calls for a new framework to study learning from a more biologically oriented perspective that integrated the evolutionary history and innate predispositions of the species. These predispositions were described as biological “constraints” on, “preparedness,” or “adaptive specializations” for learning, all of which were consistent with the “instincts to learn” framework proposed by ethologists.

By the 1980s it was becoming clear that the biological preparedness/constraint view of learning suffered some limitations. For example, what constraints count as “biological” was questioned. It was well established that there were general constraints on learning associated with the intensity, novelty, and timing of stimuli. But, arbitrarily it seemed, these constraints were not classified as “biological” (Domjan & Galef, 1983 ). Other studies of “biological constraints” found that 5- and 10-day old rats readily learned to associated a flavor with shock (unlike in adults), but (like in adults) such conditioning was not found in 15-day-old rats (Hoffman & Spear, 1988 ). In other words, the constraint on learning was not present in young rats but developed later in life, suggesting a possible role of experience in bringing about the adult-like pattern.

Attempts to synthesize these alternatives led to numerous calls for more ecologically oriented approaches to learning not unlike the synthesis between ethology and comparative psychology in the 1960s. All ecological approaches to learning proposed that learning should be studied in the context of “natural” (recurrent and species-typical) problems that animals encounter (and have evolved to encounter) using ecologically meaningful stimuli and responses. Some argued (e.g., Johnston, 1981 ) that studies of learning should take place within the larger context of studying how animals develop and adapt to their surround. Others (Domjan & Galef, 1983 ) pointed to more of a comparative approach in studying animal learning in line with behavioral ecology that takes into account how learning can be influenced by the possible selective pressures faced by each species. Still, how to synthesize biological constraints (and evolutionary explanations) on learning with a general process approach remains a source of tension in experimental psychology.

Nativism in Mind: Innate Ideas

Nativism and empiricism in philosophy.

In the philosophy of mind, nature–nurture debates are voiced as debates between nativists and empiricists. Nativism is a philosophical position that holds that our minds have some innate (a priori to experience) knowledge, concepts, or structure at the very start of life. Empiricism, in contrast, holds that all knowledge derives from our experiences in the world.

However, rarely (if ever) were there pure nativist or empiricist positions, but the positions bespeak a persistent tension. Empiricists tended to eschew innateness and promote a view of the mental content that is built by general mechanisms (e.g., association) operating on sensory experiences, whereas nativists tend to promote a view of mind that contains domain-specific, innate processes and/or content (Simpson, Carruthers, Laurence, & Stich, 2005 ). Although the tension about mental innateness would loosen as empiricism gained prominence in philosophy and science, the strain never went away and would intensify again in the 20th century .

Nativism in 20th Century Psychology: The Case of Language Development

In the first half of the 20th century , psychologists generally assumed that knowledge was gained or constructed through experience with the world. This is not to say that psychologists did not assume some innate knowledge. The Swiss psychologist Jean Piaget, for example, believed infants enter the world with some innate knowledge structures, particularly as they relate to early sensory and motor functioning (see Piaget, 1971 ). But the bulk of his work dealt with the construction of conceptual knowledge as children adapt to their worlds. By and large, there were no research programs in psychology that sought to identify innate factors in human knowledge and cognition until the 1950s (Samet & Zaitchick, 2017 )

An interest in psychological nativism was instigated in large part by Noam Chomsky’s ( 1959 ) critique of B. F. Skinner’s book on language. To explain the complexity of language, he argued, we must view language as the knowledge and application of grammatical rules. He went on to claim that the acquisition of these rules could not be attributed to any general-purpose, learning process (e.g., reinforcement). Indeed, language acquisition occurs despite very little explicit instruction. Moreover, language is special in terms of its complexity, ease, and speed of acquisition by children and in its uniqueness to humans. Instead, he claimed that our minds innately contain some language-specific knowledge that kick-starts and promotes language acquisition. He later claimed this knowledge can be considered some sort of specialized mental faculty or module he called the “language acquisition device” (Chomsky, 1965 ) or what Pinker ( 1995 ) later called the “language instinct.”

To support the idea of linguistic nativism, Chomsky and others appealed to the poverty of the stimulus argument. In short, this argument holds that our experiences in life are insufficient to explain our knowledge and abilities. When applied to language acquisition, this argument holds children’s knowledge of language (grammar) goes far beyond the limited, and sometimes broken, linguistic events that children directly encounter. Additional evidence for nativism drew upon the apparent maturational quality of language development. Despite wide variations in languages and child-rearing practices across the world, the major milestones in language development appear to unfold in children in a universal sequence and timeline, and some evidence suggested a critical period for language acquisition.

Nativist claims about language sparked intense rebuttals by empiricist-minded psychologists and philosophers. Some of these retorts tackled the logical limitations of the poverty of stimulus argument. Others pointed to the importance of learning and social interaction in driving language development, and still others showed that language (grammatical knowledge) may not be uniquely human (see Tomasello, 1995 , for review). Nativists, in due course, provided their own rebuttals to these challenges, creating a persistent tension in psychology.

Extending Nativism Beyond Language Development

In the decades that followed, nativist arguments expanded beyond language to include cognitive domains that dealt with understanding the physical, psychological, and social worlds. Developmental psychologists were finding that infants appeared to be much more knowledgeable in cognitive tasks (e.g., on understanding object permanence) and skillful (e.g., in imitating others) than had previously been thought, and at much younger ages. Infants also showed a variety of perceptual biases (e.g., preference for face-like stimuli over equally complex non-face-like stimuli) from very early on. Following the standard poverty of the stimulus argument, these findings were taken as evidence that infants enter the world with some sort of primitive, innate, representational knowledge (or domain-specific neural mechanisms) that constrains and promotes subsequent cognitive development. The nature of this knowledge (e.g., as theories or as core knowledge), however, continues to be debated (Spelke & Kinzler, 2007 ).

Empiricist-minded developmental psychologists responded by demonstrating shortcomings in the research used to support nativist claims. For example, in studies of infants’ object knowledge, the behavior of infants (looking time) in nativist studies could be attributed to relatively simple perceptual processes rather than to the infants’ conceptual knowledge (Heyes, 2014 ). Likewise, reports of human neonatal imitation not only suffered from failures to replicate but could be explained by simpler mechanisms (e.g., arousal) than true imitation (Jones, 2017 ). Finally, studies of perceptual preferences found in young infants, like newborn preferences for face-like stimuli, may not be specific preferences for faces per se but instead may reflect simpler, nonspecific perceptual biases (e.g., preferences for top-heavy visual configurations and congruency; Simion & Di Giorgio, 2015 ).

Other arguments from empiricist-minded developmental psychologists focused on the larger rationale for inferring innateness. Even if it is conceded that young infants, like two-month-olds, or even two-day-olds, display signs of conceptual knowledge, there is no good evidence to presume the knowledge is innate. Their knowledgeable behaviors could still be seen as resulting from their experiences (many of which may be nonobvious to researchers) leading up to the age of testing (Spencer et al., 2009 ).

In the 21st century , there is still no consensus about the reality, extensiveness, or quality of mental innateness. If there is innate knowledge, can experience add new knowledge or only expand the initial knowledge? Can the doctrine of innate knowledge be falsified? There are no agreed-upon answers to these questions. The recurring arguments for and against mental nativism continue to confound developmental psychologists.

Maturation Theory

The emergence of bodily changes and basic behavioral skills sometimes occurs in an invariant, predictable, and orderly sequence in a species despite wide variations in rearing conditions. These observations are often attributed to the operation of an inferred, internally driven, maturational process. Indeed, 21st-century textbooks in psychology commonly associate “nature” with “maturation,” where maturation is defined as the predetermined unfolding of the individual from a biological or genetic blueprint. Environmental factors play a necessary, but fundamentally supportive, role in the unfolding of form.

Preformationism Versus Epigenesis in the Generation of Form

The embryological generation of bodily form was debated in antiquity but received renewed interest in the 17th century . Following Aristotle, some claimed that embryological development involved “epigenesis,” defined as the successive emergence of form from a formless state. Epigenesists, however, struggled to explain what orchestrated development without appealing to Aristotelean souls. Attempts were made to invoke to natural causes like physical and chemical forces, but, despite their best efforts, the epigenesists were forced to appeal to the power of presumed, quasi-mystical, vitalistic forces (entelechies) that directed development.

The primary alternative to epigenesis was “preformationism,” which held that development involved the growth of pre-existing form from a tiny miniature (homunculus) that formed immediately after conception or was preformed in the egg or sperm. Although it seems reasonable to guess that the invention and widespread use of the microscope would immediately lay to rest any claim of homuncular preformationism, this was not the case. To the contrary, some early microscopists claimed to see signs of miniature organisms in sperm or eggs, and failures to find these miniatures were explained away (e.g., the homunculus was transparent or deflated to the point of being unrecognizable). But as microscopes improved and more detailed observations of embryological development were reported in the late 18th and 19th centuries , homuncular preformationism was finally refuted.

From Preformationism to Predeterminism

Despite the rejection of homuncular preformationism, preformationist appeals can be found throughout the 19th century . One of the most popular preformationist theories of embryological development was put forth by Ernst Haeckel in the 1860s (Gottlieb, 1992 ). He promoted a recapitulation theory (not original to Haeckel) that maintained that the development of the individual embryo passes through all the ancestral forms of its species. Ontogeny was thought to be a rapid, condensed replay of phylogeny. Indeed, for Haeckel, phylogenesis was the mechanical cause of ontogenesis. The phylogenetic evolution of the species created the maturational unfolding of embryonic form. Exactly how this unfolding takes place was less important than its phylogenetic basis.

Most embryologists were not impressed with recapitulation theory. After all, the great embryologist Karl Ernst von Baer ( 1792–1876 ) had refuted strict recapitulation decades earlier. Instead, there was greater interest in how best to explain the mechanical causes of development ushering in a new “experimental embryology.” Many experimental embryologists followed the earlier epigenesists by discussing vitalistic forces operating on the unorganized zygote. But it soon became clear that the zygote was structured, and many people believed the zygote contained special (unknown) substances that specified development. Epigenesis-minded experimental embryologists soon warned that the old homuncular preformationism was being transformed into a new predetermined preformationism.

As a result, the debates between preformationism and epigenesis were reignited in experimental embryology, but the focus of these debates shifted to the various roles of nature and nurture during development. More specifically, research focused on the extent to which early cellular differentiation was predetermined by factors internal to cells like chromosomes or cytoplasm (preformationism, nature) or involved factors (e.g., location) outside of the cell (epigenesis, nurture). The former emphasized reductionism and developmental programming, whereas the latter emphasized some sort of holistic, regulatory system responsive to internal and external conditions. The tension between viewing development as predetermined or “epigenetic” persists into the 21st century .

Preformationism gained momentum in the 20th century following the rediscovery of Mendel’s studies of heredity and the rapid rise of genetics, but not because of embryological research on the causes of early differentiation. Instead, preformationism prevailed because it seemed embryological research on the mechanisms of development could be ignored in studies of hereditary patterns.

The initial split between heredity and development can be found in Galton’s speculations but is usually attributed to Weismann’s germ-plasm theory. Weismann’s barrier seemed to posit that the germinal determinants present at conception would be the same, unaltered determinants transmitted during reproduction. This position, later dubbed as “Weismannism,” was ironically not one promoted by Weismann. Like nearly all theorists in the 19th century , he viewed the origins of variation and heredity as developmental phenomena (Amundson, 2005 ), and he claimed that the germ-plasm could be directly modified in the lifetime of the organism by environmental (e.g., climactic and dietary) conditions (Winther, 2001 ). Still, Weismann’s theory treated development as a largely predetermined affair driven by inherited, germinal determinants buffered from most developmental events. As such, it helped set the stage for a more formal divorce between heredity and development with the rise of Mendelism in the early 20th century .

Mendel’s theory of heredity was exceptional in how it split development from heredity (Amundson, 2005 ). More so than in Weismann’s theory, Mendel’s theory assumed that the internal factors that determine form and are transmitted across generations remain unaltered in the lifetime of the organism. To predict offspring outcomes, one need only know the combination of internal factors present at conception and their dominance relations. Exactly how these internal factors determined form could be disregarded. The laws of hereditary transmission of the internal factors (e.g., segregation) did not depend on the development or experiences of the organism or the experiences the organism’s ancestors. Thus the experimental study of heredity (i.e., breeding) could proceed without reference to ancestral records or embryological concerns (Amundson, 2000 ). By the mid-1920s, the Mendelian factors (now commonly called “genes”) were found to be structurally arranged on chromosomes, and the empirical study of heredity (transmission genetics) was officially divorced from studies of development.

The splitting of heredity and development found in Mendel’s and Weismann’s work met with much resistance. Neo-Lamarckian scientists, especially in the United States (Cook, 1999 ) and France (Loison, 2011 ), sought unsuccessfully to experimentally demonstrate the inheritance of acquired characteristics into the 1930s.

In Germany during the 1920s and 1930s, resistance to Mendelism dealt with the chromosomal view of Mendelian heredity championed by American geneticists who were narrowly focused on studying transmission genetics at the expense of developmental genetics. German biologists, in contrast, were much more interested in the broader roles of genes in development (and evolution). In trying to understand how genes influence development, particularly of traits of interest to embryologists, they found the Mendelian theory to be lacking. In the decades between the world wars, German biologists proposed various expanded views of heredity that included some form of cytoplasmic inheritance (Harwood, 1985 ).

Embryologists resisted the preformationist view of development throughout the early to mid- 20th century , often maintaining no divide between heredity and development, but their objections were overshadowed by genetics and its eventual synthesis with evolutionary theory. Consequently, embryological development was treated by geneticists and evolutionary biologists as a predetermined, maturational process driven by internal, “genetic” factors buffered from environmental influence.

Maturation Theory in Psychology

Maturation theory was applied to behavioral development in the 19th century in the application of Haeckel’s recapitulation theory. Some psychologists believed that the mental growth of children recapitulated the history of the human race (from savage brute to civilized human). With this in mind, many people began to more carefully document child development. Recapitulationist notions were found in the ideas of many notable psychologists in the 19th and early 20th centuries (e.g., G. S. Hall), and, as such, the concept played an important role in the origins of developmental psychology (Koops, 2015 ). But for present purposes what is most important is that children’s mental and behavioral development was thought to unfold via a predetermined, maturational process.

With the growth of genetics, maturational explanations were increasingly invoked to explain nearly all native and hereditary traits. As the instinct concept lost value in the 1920s, maturation theory gained currency, although the shift was largely a matter of semantics. For many psychologists, the language simply shifted from “instinct versus learning” to “maturation versus practice/experience” (Witty & Lehman, 1933 ).

Initial lines of evidence for maturational explanations of behavior were often the same as those that justified instinct and native traits, but new embryological research presented in the mid-1920s converged to show support for strict maturational explanations of behavioral development. In these experiments (see Wyman, 2005 , for review), spanning multiple laboratories, amphibians (salamanders and frogs) were exposed to drugs that acted as anesthetics and/or paralytics throughout the early stages of development, thus reducing sensory experience and/or motor practice. Despite the reduced sensory experiences and being unable to move, these animals showed no delays in the onset of motor development once the drugs wore off.

This maturational account of motor development in amphibians fit well with contemporaneous studies of motor development in humans. The orderly, invariant, and predictable (age-related) sequential appearance of motor skills documented in infants reared under different circumstances (in different countries and across different decades) was seen as strong evidence for a maturational account. Additional evidence was reported by Arnold Gessell and Myrtle McGraw, who independently presented evidence in the 1920s to show that the pace and sequence of motor development in infancy were not altered by special training experiences. Although the theories of these maturation theorists were more sophisticated when applied to cognitive development, their work promoted a view in which development was primarily driven by neural maturation rather than experience (Thelen, 2000 ).

Critical and Sensitive Periods

As the maturation account of behavioral development gained ground, it became clear that environmental input played a more informative role than had previously been thought. Environmental factors were found to either disrupt or induce maturational changes at specific times during development. Embryological research suggested that there were well-delineated time periods of heightened sensitivity in which specific experimental manipulations (e.g., tissue transplantations) could induce irreversible developmental changes, but the same manipulation would have no effect outside of that critical period.

In the 1950s–1960s a flurry of critical period effects were reported in birds and mammals across a range of behaviors including imprinting, attachment, socialization, sensory development, bird song learning, and language development (Michel & Tyler, 2005 ). Even though these findings highlighted an important role of experience in behavioral development, evidence of critical periods was usually taken to imply some rigid form of biological determinism (Oyama, 1979 ).

As additional studies were conducted on critical period effects, it became clear that many of the reported effects were more gradual, variable, experience-dependent, and not necessarily as reversible as was previously assumed. In light of these reports, there was a push in the 1970s (e.g., Connolly, 1972 ) to substitute “sensitive period” for “critical period” to avoid the predeterminist connotations associated with the latter and to better appreciate that these periods simply describe (not explain) certain temporal aspects of behavioral development. As a result, a consensus emerged that behaviors should not be attributed to “time” or “age” but to the developmental history and status of the animal under investigation (Michel & Tyler, 2005 ).

Heredity and Genetics

In the decades leading up to and following the start of the 20th century , it was widely assumed that many psychological traits (not just instincts) were inherited or “due to heredity,” although the underlying mechanisms were unknown. Differences in intelligence, personality, and criminality within and between races and sexes were largely assumed to be hereditary and unalterable by environmental intervention (Gould, 1996 ). The evidence to support these views in humans was often derived from statistical analyses of how various traits tended to run in families. But all too frequently, explanations of data were clouded by pre-existing, hereditarian assumptions.

Human Behavioral Genetics

The statistical study of inherited human (physical, mental, and behavioral) differences was pioneered by Galton ( 1869 ). Although at times Galton wrote that nature and nurture were so intertwined as to be inseparable, he nevertheless devised statistical methods to separate their effects. In the 1860s and 1870s, Galton published reports purporting to show how similarities in intellect (genius, talent, character, and eminence) in European lineages appeared to be a function of degree of relatedness. Galton considered, but dismissed, environmental explanations of his data, leading him to confirm his belief that nature was stronger than nurture.

Galton also introduced the use of twin studies to tease apart the relative impact of nature versus nurture, but the twin method he used was markedly different from later twin studies used by behavioral geneticists. Galton tracked the life history of twins who were judged to be very similar or very dissimilar near birth (i.e., by nature) to test the power of various postnatal environments (nurture) that might make them more or less similar over time. Here again, Galton concluded that nature overpowers nurture.

Similar pedigree (e.g., the Kallikak study; see Zenderland, 2001 ) and twin studies appeared in the early 1900s, but the first adoption study and the modern twin method (which compares monozygotic to dizygotic twin pairs) did not appear until the 1920s (Rende, Plomin, & Vandenberg, 1990 ). These reports led to a flurry of additional work on the inheritance of mental and behavioral traits over the next decade.

Behavioral genetic research peaked in the 1930s but rapidly lost prominence due in large part to its association with the eugenics movement (spearheaded by Galton) but also because of the rise and eventual hegemony of behaviorism and the social sciences in the United States. Behavioral genetics resurged in the 1960s with the rising tide of nativism in psychology, and returned to its 1930s-level prominence in the 1970s (McGue & Gottesman, 2015 ).

The resurgence brought with a new statistical tool: the heritability statistic. The origins of heritability trace back to early attempts to synthesize Mendelian genetics with biometrics by Ronald Fisher and others. This synthesis ushered in a new field of quantitative genetics and it marked a new way of thinking about nature and nurture. The shift was to no longer think about nature and nurture as causes of traits in individuals but as causes of variation in traits between populations of individuals. Eventually, heritability came to refer to the amount of variance in a population sample that could be statistically attributed to genetic variation in that sample. Kinship (especially twin) studies provided seemingly straightforward ways of partitioning variation in population trait attributes into genetic versus environmental sources.

Into the early 21st century , hundreds of behavioral genetic studies of personality, intelligence, and psychopathology were reported. With rare exceptions, these studies converge to argue for a pervasive influence of genetics on human psychological variation.

These studies have also fueled much controversy. Citing in part behavioral genetic research, the educational psychologist Arthur Jensen ( 1969 ) claimed that the differences in intelligence and educational achievement in the United States between black and white students appeared to have a strong genetic basis. He went on to assume that because these racial differences appeared hereditary, they were likely impervious to environmental (educational) intervention. His article fanned the embers of past eugenics practices and ignited fiery responses (e.g., Hirsch, 1975 ). The ensuing debates not only spawned a rethinking of intelligence and how to measure it, but they ushered in a more critical look at the methods and assumptions of behavioral genetics.

Challenges to Behavioral Genetics

Many of the early critiques of behavioral genetics centered on interpreting the heritability statistic commonly calculated in kinship (family, twin, and adoption) studies. Perhaps more so than any other statistic, heritability has been persistently misinterpreted by academics and laypersons alike (Lerner, 2002 ). Contrary to popular belief, heritability tells us nothing about the relative impact of genetic and environmental factors on the development of traits in individuals. It deals with accounting for trait variation between people, not the causes of traits within people. As a result, a high heritability does not indicate anything about the fixity of traits or their imperviousness to environmental influence (contra Jensen), and a low heritability does not indicate an absence of genetic influence on trait development. Worse still, heritability does not even indicate anything about the role of genetics in generating the differences between people.

Other challenges to heritability focused not on its interpretation but on its underlying computational assumptions. Most notably, heritability analyses assume that genetic and environmental contributions to trait differences are independent and additive. The interaction between genetic and environmental factors were dismissed a priori in these analyses. Studies of development, however, show that no factor (genes, hormones, parenting, schooling) operates independently, making it impossible to quantify how much of a given trait in a person is due to any causal factor. Thus heritability analyses are bound to be misleading because they are based on biologically implausible and logically indefensible assumptions about development (Gottlieb, 2003 ).

Aside from heritability, kinship studies have been criticized for not being able to disentangle genetic and environmental effects on variation. It had long been known that that in family (pedigree) studies, environmental and genetic factors are confounded. Twin and adoption studies seemed to provide unique opportunities to statistically disentangle these effects, but these studies are also deeply problematic in assumptions and methodology. There are numerous plausible environmental reasons for why monozygotic twin pairs could resemble each other more than dizygotic twin pairs or why adoptive children might more closely resemble their biological than their adoptive parents (Joseph & Ratner, 2013 ).

A more recent challenge to behavioral genetics came from an unlikely source. Advances in genomic scanning in the 21st century made it possible in a single study to correlate thousands of genetic polymorphisms with variation in the psychological profiles (e.g., intelligence, memory, temperament, psychopathology) of thousands of people. These “genome-wide association” studies seemed to have the power and precision to finally identify genetic contributions to heritability at the level of single nucleotides. Yet, these studies consistently found only very small effects.

The failure to find large effects came to be known as the “missing heritability” problem (Maher, 2008 ). To account for the missing heritability, some behavioral geneticists and molecular biologists asserted that important genetic polymorphisms remain unknown, they may be too rare to detect, and/or that current studies are just not well equipped to handle gene–gene interactions. These studies were also insensitive to epigenetic profiles (see the section on Behavioral Epigenetics), which deal with differences in gene expression. Even when people share genes, they may differ in whether those genes get expressed in their lifetimes.

But genome-wide association studies faced an even more problematic issue: Many of these studies failed to replicate (Lickliter & Honeycutt, 2015 ). For those who viewed heritability analyses as biologically implausible, the small effect sizes and failures to replicate in genome-wide association studies were not that surprising. The search for independent genetic effects was bound to fail, because genes simply do not operate independently during development.

Behavioral Epigenetics

Epigenetics was a term coined in the 1940s by the developmental biologist Conrad Waddington to refer to a new field of study that would examine how genetic factors interact with local environmental conditions to bring about the embryological development of traits. By the end of the 20th century , epigenetics came to refer to the study of how nongenetic, molecular mechanisms physically regulate gene expression patterns in cells and across cell lineages. The most-studied mechanisms involve organic compounds (e.g., methyl-groups) that physically bind to DNA or the surrounding proteins that package DNA. The addition or removal of these compounds can activate or silence gene transcription. Different cell types have different, stable epigenetic markings, and these markings are recreated during cell division so that cells so marked give rise to similar types of cells. Epigenetic changes were known to occur during developmental periods of cellular differentiation (e.g., during embryogenesis), but not until 2004 was it discovered that these changes can occur at other periods in the life, including after birth (Roth, 2013 )

Of interest to psychologists were reports that different behavioral and physiological profiles (e.g., stress reactivity) of animals were associated with different epigenetic patterns in the nervous system (Moore, 2015 ). Furthermore, these different epigenetic patterns could be established or modified by environmental factors (e.g., caregiving practices, training regimes, or environmental enrichment), and, under certain conditions, they remain stable over long periods of time (from infancy to adulthood).

Because epigenetic research investigates the physical interface between genes and environment, it represents an exciting advance in understanding the interaction of nature and nurture. Despite some warnings that the excitement over behavioral epigenetic research may be premature (e.g., Miller, 2010 ), for many psychologists, epigenetics underscores how development involves both nature and nurture.

For others, what is equally exciting is the additional evidence epigenetics provides to show that the genome is an interactive and regulated system. Once viewed as the static director of development buffered from environment influence, the genome is better described as a developing resource of the cell (Moore, 2015 ). More broadly, epigenetics also points to how development is not a genetically (or biologically) predetermined affair. Instead, epigenetics provides additional evidence that development is a probabilistic process, contingent upon factors internal and external to the organism. In this sense, epigenetics is well positioned to help dissolve the nature–nurture dichotomy.

Beyond Nature–Nurture

In the final decades of the 20th century , a position was articulated to move beyond the dichotomous nature–nurture framework. The middle-ground position on nature–nurture did not seem up to the task of explaining the origins of form, and it brought about more confusion than clarity. The back-and-forth (or balanced) pendulum between nature- and nurture-based positions throughout history had only gone in circles. Moving forward would require moving beyond such dichotomous thinking (Johnston, 1987 ).

The anti-dichotomy position, referred to as the Developmentalist tradition, was expressed in a variety of systems-based, metatheoretical approaches to studying development, all of which extended the arguments against nature–nurture expressed earlier by Kuo and Lehrman. The central problem with all nativist claims according to Developmentalists is a reliance on preformationism (or predeterminism).

The problem with preformationism, they argue, besides issues of evidence, is that it is an anti-developmental mindset. It presumes the existence of the very thing(s) one wishes to explain and, consequently, discourages developmental analyses. To claim that some knowledge is innate effectively shuts down research on the developmental origins of that knowledge. After all, why look for the origins of conceptual knowledge if that knowledge is there all along? Or why search for any experiential contributions to innate behaviors if those behaviors by definition develop independently of experience? In the words of Developmentalists Thelen and Adolph ( 1992 ), nativism “leads to a static science, with no principles for understanding change or for confronting the ultimate challenge of development, the source of new forms in structure and function” (p. 378).

A commitment to maturational theory is likely one of the reasons why studies of motor development remained relatively dormant for decades following its heyday in the 1930–1940s (Thelen, 2000 ). Likewise, a commitment to maturational theory also helps explain the delay in neuroscience to examine how the brain physically changes in response to environmental conditions, a line of inquiry that only began in the 1960s.

In addition to the theoretical pitfalls of nativism, Developmentalists point to numerous studies that show how some seemingly native behaviors and innate constraints on learning are driven by the experiences of animals. For example, the comparative psychologist Gilbert Gottlieb ( 1971 ) showed that newly hatched ducklings display a naïve preference for a duck maternal call over a (similarly novel) chicken maternal call (Gottlieb, 1971 ), even when duck embryos were repeatedly exposed to the chicken call prior to hatching (Gottlieb, 1991 ). It would be easy to conclude that ducklings have an innate preference to approach their own species call and that they are biologically constrained (contraprepared) in learning a chicken call. However, Gottlieb found that the naïve preference for the duck call stemmed from exposure to the duck embryos’ own (or other) vocalizations in the days before hatching (Gottlieb, 1971 ). Exposure to these vocalizations not only made duck maternal calls more attractive, but it hindered the establishment of a preference for heterospecific calls. When duck embryos were reared in the absence of the embryonic vocalizations (by devocalizing embryos in ovo ) and exposed instead to chicken maternal calls, the newly hatched ducklings preferred chicken over duck calls (Gottlieb, 1991 ). These studies clearly showed how seemingly innate, biologically based preferences and constraints on learning derived from prenatal sensory experiences.

For Developmentalists, findings like these suggest that nativist explanations of any given behavior are statements of ignorance about how that behavior actually develops. As Kuo and Lehrman made clear, nativist terms are labels, not explanations. Although such appeals are couched in respectable, scientific language (e.g., “X is due to maturation, genes, or heredity”), they argue it would be more accurate simply to say that “We don’t know what causes X” or that “X is not due to A, B, or C.” Indeed, for Developmentalists, the more we unpack the complex dynamics about how traits develop, the less likely we are to use labels like nature or nurture (Blumberg, 2005 ).

On the other hand, Developmentalists recognize that labeling a behavior as “learned” also falls short as an explanatory construct. The empiricist position that knowledge or behavior is learned does not adequately take into account that what is learned and how easily something is learned depends on (a) the physiological and developmental status of the person, (b) the nature of the surrounding physical and social context in which learning takes place, and the (c) experiential history of the person. The empiricist tendency to say “X is learned or acquired through experience” can also short-circuit developmental analyses in the same way as nativist claims.

Still, Developmentalists appreciate that classifying behaviors can be useful. For example, the development of some behaviors may be more robust, reliably emerging across a range of environments and/or remaining relatively resistant to change, whereas others are more context-specific and malleable. Some preferences for stimuli require direct experience with those stimuli. Other preferences require less obvious (indirect) types of experiences. Likewise, it can still be useful to describe some behaviors in the ways shown in Table 1 . Developmentalists simply urge psychologists to resist the temptation to treat these behavioral classifications as implying different kinds of explanations (Johnston, 1987 ).

Rather than treat nature and nurture as separate developmental sources of causation (see Figure 1 ), Developmentalists argue that a more productive way of thinking about nature–nurture is to reframe the division as that between product and process (Lickliter & Honeycutt, 2015 ). The phenotype or structure (one’s genetic, epigenetic, anatomical, physiological, behavioral, and mental profile) of an individual at any given time can be considered one’s “nature.” “Nurture” then refers to the set of processes that generate, maintain, and transform one’s nature (Figure 2 ). These processes involve the dynamic interplay between phenotypes and environments.

Figure 2. The developmentalist alternative view of nature–nurture as product–process. Developmentalists view nature and nurture not as separate sources of causation in development (see Figure 1 ) but as a distinction between process (nurture) and product (nature).

It is hard to imagine any set of findings that will end debates about the roles of nature and nurture in human development. Why? First, more so than other assumptions about human development, the nature–nurture dichotomy is deeply entrenched in popular culture and the life sciences. Second, throughout history, the differing positions on nature and nurture were often driven by other ideological, philosophical, and sociopolitical commitments. Thus the essential source of tension in debates about nature–nurture is not as much about research agendas or evidence as about basic differences in metatheoretical positions (epistemological and ontological assumptions) about human behavior and development (Overton, 2006 ).

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Human Nature

Talk of human nature is a common feature of moral and political discourse among people on the street and among philosophers, political scientists and sociologists. This is largely due to the widespread assumption that true descriptive or explanatory claims making use of the concept of human nature have, or would have, considerable normative significance. Some think that human nature excludes the possibility of certain forms of social organisation—for example, that it excludes any broadly egalitarian society. Others make the stronger claim that a true normative ethical theory has to be built on prior knowledge of human nature. Still others believe that there are specific moral prohibitions concerning the alteration of, or interference in, the set of properties that make up human nature. Finally, there are those who argue that the normative significance derives from the fact that merely deploying the concept is typically, or even necessarily, pernicious.

Alongside such varying and frequently conflicting normative uses of the expression “human nature”, there are serious disagreements concerning the concept’s content and explanatory significance—the starkest being whether the expression “human nature” refers to anything at all. Some reasons given for saying there is no human nature are anthropological, grounded in views concerning the relationship between natural and cultural features of human life. Other reasons given are biological, deriving from the character of the human species as, like other species, an essentially historical product of evolution. Whether these reasons justify the claim that there is no human nature depends, at least in part, on what it is exactly that the expression is supposed to be picking out. Many contemporary proposals differ significantly in their answers to this question.

Understanding the debates around the philosophical use of the expression “human nature” requires clarity on the reasons both for (1) adopting specific adequacy conditions for the term’s use and for (2) accepting particular substantial claims made within the framework thus adopted. One obstacle to such clarity is historical: we have inherited from the beginnings of Western philosophy, via its Medieval reception, the idea that talk of human nature brings into play a number of different, but related claims. One such set of claims derives from different meanings of the Greek equivalents of the term “nature”. This bundle of claims, which can be labelled the traditional package , is a set of adequacy conditions for any substantial claim that uses the expression “human nature”. The beginnings of Western philosophy have also handed down to us a number of such substantial claims . Examples are that humans are “rational animals” or “political animals”. We can call these claims the traditional slogans . The traditional package is a set of specifications of how claims along the lines of the traditional slogans are to be understood, i.e., what it means to claim that it is “human nature” to be, for example, a rational animal.

Various developments in Western thought have cast doubt both on the coherence of the traditional package and on the possibility that the adequacy conditions for the individual claims can be fulfilled. Foremost among these developments are the Enlightenment rejection of teleological metaphysics, the Historicist emphasis on the significance of culture for understanding human action and the Darwinian introduction of history into biological kinds. This entry aims to help clarify the adequacy conditions for claims about human nature, the satisfiability of such conditions and the reasons why the truth of claims with the relevant conditions might seem important. It proceeds in five steps. Section 1 unpacks the traditional package, paying particular attention to the importance of Aristotelian themes and to the distinction between the scientific and participant perspectives from which human nature claims can be raised. Section 2 explains why evolutionary biology raises serious problems both for the coherence of this package and for the truth of its individual component claims. Sections 3 and 4 then focus on attempts to secure scientific conceptions of human nature in the face of the challenge from evolutionary biology. The entry concludes with a discussion of accounts of human nature developed from a participant perspective, in particular accounts that, in spite of the evolutionary challenge, are taken to have normative consequences.

1.1 “Humans”

1.2 unpacking the traditional package, 1.3 essentialisms, 1.4 on the status of the traditional slogan, 2.1 the nature of the species taxon, 2.2 the nature of species specimens as species specimens, 2.3 responding to the evolutionary verdict on classificatory essences, 3.1 privileging properties, 3.2 statistical normality or robust causality, 4.1 genetically based psychological adaptations, 4.2 abandoning intrinsicality, 4.3 secondary altriciality as a game-changer, 5.1. human nature from a participant perspective, 5.2.1. sidestepping the darwinian challenge, 5.2.2. human flourishing, 5.3. reason as the unique structural property, other internet resources, related entries, 1. “humans”, slogans and the traditional package.

Before we begin unpacking, it should be noted that the adjective “human” is polysemous, a fact that often goes unnoticed in discussions of human nature, but makes a big difference to both the methodological tractability and truth of claims that employ the expression. The natural assumption may appear to be that we are talking about specimens of the biological species Homo sapiens , that is, organisms belonging to the taxon that split from the rest of the hominin lineage an estimated 150,000 years ago. However, certain claims seem to be best understood as at least potentially referring to organisms belonging to various older species within the subtribe Homo , with whom specimens of Homo sapiens share properties that have often been deemed significant (Sterelny 2018: 114).

On the other hand, the “nature” that is of interest often appears to be that of organisms belonging to a more restricted group. There may have been a significant time lag between the speciation of anatomically modern humans ( Homo sapiens ) and the evolution of behaviourally modern humans, i.e., human populations whose life forms involved symbol use, complex tool making, coordinated hunting and increased geographic range. Behavioural modernity’s development is often believed only to have been completed by 50,000 years ago. If, as is sometimes claimed, behavioural modernity requires psychological capacities for planning, abstract thought, innovativeness and symbolism (McBrearty & Brooks 2000: 492) and if these were not yet widely or sufficiently present for several tens of thousands of years after speciation, then it may well be behaviourally, rather than anatomically modern humans whose “nature” is of interest to many theories. Perhaps the restriction might be drawn even tighter to include only contemporary humans, that is, those specimens of the species who, since the introduction of agriculture around 12,000 years ago, evolved the skills and capacities necessary for life in large sedentary, impersonal and hierarchical groups (Kappeler, Fichtel, & van Schaik 2019: 68).

It was, after all, a Greek living less than two and a half millennia ago within such a sedentary, hierarchically organised population structure, who could have had no conception of the prehistory of the beings he called anthrôpoi , whose thoughts on their “nature” have been decisive for the history of philosophical reflection on the subject. It seems highly likely that, without the influence of Aristotle, discussions of “human nature” would not be structured as they are until today.

We can usefully distinguish four types of claim that have been traditionally made using the expression “human nature”. As a result of a particular feature of Aristotle’s philosophy, to which we will come in a moment, these four claims are associated with five different uses of the expression. Uses of the first type seem to have their origin in Plato; uses of the second, third and fourth type are Aristotelian; and, although uses of the fifth type have historically been associated with Aristotle, this association seems to derive from a misreading in the context of the religiously motivated Mediaeval reception of his philosophy.

A first , thin, contrastive use of the expression “human nature” is provided by the application of a thin, generic concept of nature to humans. In this minimal variant, nature is understood in purely contrastive or negative terms. Phusis is contrasted in Plato and Aristotle with technē , where the latter is the product of intention and a corresponding intervention of agency. If the entire cosmos is taken to be the product of divine agency, then, as Plato argued (Nadaf 2005: 1ff.), conceptualisations of the cosmos as natural in this sense are mistaken. Absent divine agency, the types of agents whose intentions are relevant for the status of anything as natural are human agents. Applied to humans, then, this concept of nature picks out human features that are not the results of human intentional action. Thus understood, human nature is the set of human features or processes that remain after subtraction of those picked out by concepts of the non-natural, concepts such as “culture”, “nurture”, or “socialisation”.

A second component in the package supplies the thin concept with substantial content that confers on it explanatory power. According to Aristotle, natural entities are those that contain in themselves the principle of their own production or development, in the way that acorns contain a blueprint for their own realisation as oak trees ( Physics 192b; Metaphysics 1014b). The “nature” of natural entities thus conceptualised is a subset of the features that make up their nature in the first sense. The human specification of this explanatory concept of nature aims to pick out human features that similarly function as blueprints for something like a fully realised form. According to Aristotle, for all animals that blueprint is “the soul”, that is, the integrated functional capacities that characterise the fully developed entity. The blueprint is realised when matter, i.e., the body, has attained the level of organisation required to instantiate the animal’s living functions (Charles 2000: 320ff.; Lennox 2009: 356).

A terminological complication is introduced here by the fact that the fully developed form of an entity is itself also frequently designated as its “nature” (Aristotle, Physics 193b; Politics 1252b). In Aristotle’s teleological metaphysics, this is the entity’s end, “that for the sake of which a thing is” ( Metaphysics 1050a; Charles 2000: 259). Thus, a human’s “nature”, like that of any other being, may be either the features in virtue of which it is disposed to develop to a certain mature form or, thirdly , the form to which it is disposed to develop.

Importantly, the particularly prominent focus on the idea of a fully developed form in Aristotle’s discussions of humans derives from its dual role. It is not only the form to the realisation of which human neonates are disposed; it is also the form that mature members of the species ought to realise ( Politics 1253a). This normative specification is the fourth component of the traditional package. The second, third and fourth uses of “nature” are all in the original package firmly anchored in a teleological metaphysics. One question for systematic claims about human nature is whether any of these components remain plausible if we reject a teleology firmly anchored in theology (Sedley 2010: 5ff.).

A fifth and last component of the package that has traditionally been taken to have been handed down from antiquity is classificatory. Here, the property or set of properties named by the expression “human nature” is that property or property set in virtue of the possession of which particular organisms belong to a particular biological taxon: what we now identify as the species taxon Homo sapiens . This is human nature typologically understood.

This, then, is the traditional package:

The sort of properties that have traditionally been taken to support the classificatory practices relevant to TP5 are intrinsic to the individual organisms in question. Moreover, they have been taken to be able to fulfil this role in virtue of being necessary and sufficient for the organism’s membership of the species, i.e., “essential” in one meaning of the term. This view of species membership, and the associated view of species themselves, has been influentially dubbed “typological thinking” (Mayr 1959 [1976: 27f.]; cf. Mayr 1982: 260) and “essentialism” (Hull 1965: 314ff.; cf. Mayr 1968 [1976: 428f.]). The former characterisation involves an epistemological focus on the classificatory procedure, the latter a metaphysical focus on the properties thus singled out. Ernst Mayr claimed that the classificatory approach originates in Plato’s theory of forms, and, as a result, involves the further assumption that the properties are unchanging. According to David Hull, its root cause is the attempt to fit the ontology of species taxa to an Aristotelian theory of definition.

The theory of definition developed in Aristotle’s logical works assigns entities to a genus and distinguishes them from other members of the genus, i.e., from other “species”, by their differentiae ( Topics 103b). The procedure is descended from the “method of division” of Plato, who provides a crude example as applied to humans, when he has the Eleatic Stranger in the Statesman characterise them as featherless bipeds (266e). Hull and many scholars in his wake (Dupré 2001: 102f.) have claimed that this simple schema for picking out essential conditions for species membership had a seriously deleterious effect on biological taxonomy until Darwin (cf. Winsor 2006).

However, there is now widespread agreement that Aristotle was no taxonomic essentialist (Balme 1980: 5ff.; Mayr 1982: 150ff.; Balme 1987: 72ff.; Ereshefsky 2001: 20f; Richards 2010: 21ff.; Wilkins 2018: 9ff.). First, the distinction between genus and differentiae was for Aristotle relative to the task at hand, so that a “species” picked out in this manner could then count as the genus for further differentiation. Second, the Latin term “species”, a translation of the Greek eidos , was a logical category with no privileged relationship to biological entities; a prime example in the Topics is the species justice, distinguished within the genus virtue (143a). Third, in a key methodological passage, Parts of Animals , I.2–3 (642b–644b), Aristotle explicitly rejects the method of “dichotomous division”, which assigns entities to a genus and then seeks a single differentia, as inappropriate to the individuation of animal kinds. Instead, he claims, a multiplicity of differentiae should be brought to bear. He emphasises this point in relation to humans (644a).

According to Pierre Pellegrin and David Balme, Aristotle did not seek to establish a taxonomic system in his biological works (Pellegrin 1982 [1986: 113ff.]; Balme 1987, 72). Rather, he simply accepted the everyday common sense partitioning of the animal world (Pellegrin 1982 [1986: 120]; Richards 2010: 24; but cf. Charles 2000: 343ff.). If this is correct, Aristotle didn’t even ask after the conditions for belonging to the species Homo sapiens . So he wasn’t proposing any particular answer, and specifically not the “essentialist” answer advanced by TP5. In as far as such an answer has been employed in biological taxonomy (cf. Winsor 2003), its roots appear to lie in Neoplatonic, Catholic misinterpretations of Aristotle (Richards 2010: 34ff.; Wilkins 2018: 22ff.). Be that as it may, the fifth use of “human nature” transported by tradition—to pick out essential conditions for an organism’s belonging to the species—is of eminent interest. The systematic concern behind Mayr and Hull’s historical claims is that accounts of the form of TP5 are incompatible with evolutionary theory. We shall look at this concern in section 2 of this entry.

Because the term “essentialism” recurs with different meanings in discussions of human nature and because some of the theoretical claims thus summarised are assumed to be Aristotelian in origin, it is worth spending a moment here to register what claims can be singled out by the expression. The first , purely classificatory conception just discussed should be distinguished from a second view that is also frequently labelled “essentialist” and which goes back to Locke’s concept of “real essence” (1689: III, iii, 15). According to essentialism thus understood, an essence is the intrinsic feature or features of an entity that fulfils or fulfil a dual role: firstly, of being that in virtue of which something belongs to a kind and, secondly, of explaining why things of that kind typically have a particular set of observable features. Thus conceived, “essence” has both a classificatory and an explanatory function and is the core of a highly influential, “essentialist” theory of natural kinds, developed in the wake of Kripke’s and Putnam’s theories of reference.

An account of human nature that is essentialist in this sense would take the nature of the human natural kind to be a set of microstructural properties that have two roles: first, they constitute an organism’s membership of the species Homo sapiens . Second, they are causally responsible for the organism manifesting morphological and behavioural properties typical of species members. Paradigms of entities with such natures or essences are chemical elements. An example is the element with the atomic number 79, the microstructural feature that accounts for surface properties of gold such as yellowness. Applied to organisms, it seems that the relevant explanatory relationship will be developmental, the microstructures providing something like a blueprint for the properties of the mature individual. Kripke assumed that some such blueprint is the “internal structure” responsible for the typical development of tigers as striped, carnivorous quadrupeds (Kripke 1972 [1980: 120f.]).

As the first, pseudo-Aristotelian version of essentialism illustrates, the classificatory and explanatory components of what we might call “Kripkean essentialism” can be taken apart. Thus, “human nature” can also be understood in exclusively explanatory terms, viz. as the set of microstructural properties responsible for typical human morphological and behavioural features. In such an account, the ability to pick out the relevant organisms is simply presupposed. As we shall see in section 4 of this entry, accounts of this kind have been popular in the contemporary debate. The subtraction of the classificatory function of the properties in these conceptions has generally seemed to warrant withholding from them the label “essentialist”. However, because some authors have still seen the term as applicable (Dupré 2001: 162), we might think of such accounts as constituting a third , weak or deflationary variant of essentialism.

Such purely explanatory accounts are descendants of the second use of “human nature” in the traditional package, the difference being that they don’t usually presuppose some notion of the fully developed human form. However, where some such presupposition is made, there are stronger grounds for talking of an “essentialist” account. Elliott Sober has argued that the key to essentialism is not classification in terms of necessary and sufficient conditions, but the postulation of some “privileged state”, to the realisation of which specimens of a species tend, as long as no extrinsic factors “interfere” (Sober 1980: 358ff.). Such a dispositional-teleological conception, dissociated from classificatory ambitions, would be a fourth form of essentialism. Sober rightly associates such an account with Aristotle, citing Aristotle’s claims in his zoological writings that interfering forces are responsible for deviations, i.e., morphological differences, both within and between species. A contemporary account of human nature with this structure will be discussed in section 4 .

A fifth and final form of essentialism is even more clearly Aristotelian. Here, an explicitly normative status is conferred on the set of properties to the development of which human organisms tend. For normative essentialism, “the human essence” or “human nature” is a normative standard for the evaluation of organisms belonging to the species. Where the first, third and fourth uses of the expression have tended to be made with critical intent (for defensive exceptions, see Charles 2000: 348ff.; Walsh 2006; Devitt 2008; Boulter 2012), this fifth use is more often a self-ascription (e.g., Nussbaum 1992). It is intended to emphasise metaethical claims of a specific type. According to such claims, an organism’s belonging to the human species entails or in some way involves the applicability to the organism of moral norms that ground in the value of the fully developed human form. According to one version of this thought, humans ought be, or ought to be enabled to be, rational because rationality is a key feature of the fully developed human form. Such normative-teleological accounts of human nature will be the focus of section 5.2 .

We can summarise the variants of essentialism and their relationship to the components of the traditional package as follows:

Section 2 and section 5 of this entry deal with the purely classificatory and the normative teleological conceptions of human nature respectively, and with the associated types of essentialism. Section 3 discusses attempts to downgrade TP5, moving from essential to merely characteristic properties. Section 4 focuses on accounts of an explanatory human nature, both on attempts to provide a modernized version of the teleological blueprint model ( §4.1 ) and on explanatory conceptions with deflationary intent relative to the claims of TP2 and TP3 ( §4.2 and §4.3 ).

The traditional package specifies a set of conditions some or all of which substantial claims about “human nature” are supposed to meet. Before we turn to the systematic arguments central to contemporary debates on whether such conditions can be met, it will be helpful to spend a moment considering one highly influential substantial claim. Aristotle’s writings prominently contain two such claims that have been handed down in slogan form. The first is that the human being (more accurately: “man”) is an animal that is in some important sense social (“zoon politikon”, History of Animals 487b; Politics 1253a; Nicomachean Ethics 1169b). According to the second, “he” is a rational animal ( Politics 1253a, where Aristotle doesn’t actually use the traditionally ascribed slogan, “zoon logon echon”).

Aristotle makes both claims in very different theoretical contexts, on the one hand, in his zoological writings and, on the other, in his ethical and political works. This fact, together with the fact that Aristotle’s philosophy of nature and his practical philosophy are united by a teleological metaphysics, may make it appear obvious that the slogans are biological claims that provide a foundation for normative claims in ethics and politics. The slogans do indeed function as foundations in the Politics and the Nicomachean Ethics respectively (on the latter, see section 5 of this entry). It is, however, unclear whether they are to be understood as biological claims. Let us focus on the slogan that has traditionally dominated discussions of human nature in Western philosophy, that humans are “rational animals”.

First, if Pellegrin and Balme are right that Aristotelian zoology is uninterested in classifying species, then ascribing the capacity for “rationality” cannot have the function of naming a biological trait that distinguishes humans from other animals. This is supported by two further sets of considerations. To begin with, Aristotle’s explicit assertion that a series of differentiae would be needed to “define” humans ( Parts of Animals 644a) is cashed out in the long list of features he takes to be their distinguishing marks, such as speech, having hair on both eyelids, blinking, having hands, upright posture, breasts in front, the largest and moistest brain, fleshy legs and buttocks (Lloyd 1983: 29ff.). Furthermore, there is in Aristotle no capacity for reason that is both exclusive to, and universal among anthropoi . One part or kind of reason, “practical intelligence” ( phronesis ), is, Aristotle claims, found in both humans and other animals, being merely superior in the former ( Parts of Animals , 687a). Now, there are other forms of reasoning of which this is not true, forms whose presence are sufficient for being human: humans are the only animals capable of deliberation ( History of Animals 488b) and reasoning ( to noein ), in as far as this extends to mathematics and first philosophy. Nevertheless, these forms of reasoning are unnecessary: slaves, who Aristotle includes among humans ( Politics 1255a), are said to have no deliberative faculty ( to bouleutikon ) at all ( Politics 1260a; cf. Richter 2011: 42ff.). Presumably, they will also be without the capacities necessary for first philosophy.

Second, these Aristotelian claims raise the question as to whether the ascription of rationality is even intended as an ascription to an individual in as far as she or he belongs to a biological kind. The answer might appear to be obviously affirmative. Aristotle uses the claim that a higher level of reason is characteristic of humans to teleologically explain other morphological features, in particular upright gait and the morphology of the hands ( Parts of Animals 686a, 687a). However, the kind of reason at issue here is practical intelligence, the kind humans and animals share, not the capacity for mathematics and metaphysics, which among animals is exercised exclusively by humans. In as far as humans are able to exercise this latter capacity in contemplation, Aristotle claims that they “partake of the divine” ( Parts of Animals 656a), a claim of which he makes extensive use when grounding his ethics in human rationality ( Nicomachean Ethics 1177b–1178b). When, in a passage to which James Lennox has drawn attention (Lennox 1999), Aristotle declares that the rational part of the soul cannot be the object of natural science ( Parts of Animals 645a), it seems to be the contemplative part of the soul that is thus excluded from biological investigation, precisely the feature that is named in the influential slogan. If it is the “something divine … present in” humans that is decisively distinctive of their kind, it seems unclear whether the relevant kind is biological.

It is not the aim of this entry to decide questions of Aristotle interpretation. What is important is that the relationship of the question of “human nature” to biology is, from the beginning of the concept’s career, not as unequivocal as is often assumed (e.g., Hull 1986: 7; Richards 2010: 217f.). This is particularly true of the slogan according to which humans are rational animals. In the history of philosophy, this slogan has frequently been detached from any attempt to provide criteria for biological classification or characterisation. When Aquinas picks up the slogan, he is concerned to emphasise that human nature involves a material, corporeal aspect. This aspect is, however, not thought of in biological terms. Humans are decisively “rational substances”, i.e., persons. As such they also belong to a kind whose members also number angels and God (three times) (Eberl 2004). Similarly, Kant is primarily, indeed almost exclusively, interested in human beings as examples of “rational nature”, “human nature” being only one way in which rational nature can be instantiated (Kant 1785, 64, 76, 85). For this reason, Kant generally talks of “rational beings”, rather than of “rational animals” (1785, 45, 95).

There is, then, a perspective on humans that is plausibly present in Aristotle, stronger in Aquinas and dominant in Kant and that involves seeing them as instances of a kind other than the “human kind”, i.e., seeing the human animal “as a rational being” (Kant 1785 [1996: 45]). According to this view, the “nature” of humans that is most worthy of philosophical interest is the one they possess not insofar as they are human, but insofar as they are rational. Where this is the relevant use of the concept of human nature, being a specimen of the biological species is unnecessary for possessing the corresponding property. Specimens of other species, as well as non-biological entities may also belong to the relevant kind. It is also insufficient, as not all humans will have the properties necessary for membership in that kind.

As both a biologist and ethicist, Aristotle is at once a detached scientist and a participant in forms of interpersonal and political interaction only available to contemporary humans living in large, sedentary subpopulations. It seems plausible that a participant perspective may have suggested a different take on what it is to be human, perhaps even a different take on the sense in which humans might be rational animals, to that of biological science. We will return to this difference in section 5 of the entry.

2. The Nature of the Evolutionary Unit Homo sapiens and its Specimens

Detailing the features in virtue of which an organism is a specimen of the species Homo sapiens is a purely biological task. Whether such specification is achievable and, if so how, is controversial. It is controversial for the same reasons for which it is controversial what conditions need to be met for an organism to be a specimen of any species. These reasons derive from the theory of evolution.

A first step to understanding these reasons involves noting a further ambiguity in the use of the expression “human nature”, this time an ambiguity specific to taxonomy. The term can be used to pick out a set of properties as an answer to two different questions. The first concerns the properties of some organism which make it the case that it belongs to the species Homo sapiens . The second concerns the properties in virtue of which a population or metapopulation is the species Homo sapiens . Correspondingly, “human nature” can pick out either the properties of organisms that constitute their partaking in the species Homo sapiens or the properties of some higher-level entity that constitute it as that species. Human nature might then either be the nature of the species or the nature of species specimens as specimens of the species.

It is evolution that confers on this distinction its particular form and importance. The variation among organismic traits, without which there would be no evolution, has its decisive effects at the level of populations. These are groups of organisms that in some way cohere at a time in spite of the variation of traits among the component organisms. It is population-level groupings, taxa, not organisms, that evolve and it is taxa, such as species, that provide the organisms that belong to them with genetic resources (Ghiselin 1987: 141). The species Homo sapiens appears to be a metapopulation that coheres at least in part because of the gene flow between its component organisms brought about by interbreeding (cf. Ereshefsky 1991: 96ff.). Hence, according to evolutionary theory, Homo sapiens is plausibly a higher-level entity—a unit of evolution—consisting of the lower-level entities that are individual human beings. The two questions phrased in terms of “human nature” thus concern the conditions for individuation of the population-level entity and the conditions under which organisms are components of that entity.

The theory of evolution transforms the way we should understand the relationship between human organisms and the species to which they belong. The taxonomic assumption of TP5 was that species are individuated by means of intrinsic properties that are individually instantiated by certain organisms. Instantiating those properties is taken to be necessary and sufficient for those organisms to belong to the species. Evolutionary theory makes it clear that species, as population-level entities, cannot be individuated by means of the properties of lower-level constituents, in our case, of individual human organisms (Sober 1980: 355).

The exclusion of this possibility grounds a decisive difference from the way natural kinds are standardly construed in the wake of Locke and Kripke. Recall that, in this Kripkean construal, lumps of matter are instances of chemical kinds because of their satisfaction of intrinsic necessary and sufficient conditions, viz. their atoms possessing a certain number of protons. The same conditions also individuate the chemical kinds themselves. Chemical kinds are thus spatiotemporally unrestricted sets. This means that there are no metaphysical barriers to the chance generation of members of the kind, independently of whether the kind is instantiated at any contiguous time or place. Nitrogen could come to exist by metaphysical happenstance, should an element with the atomic number 14 somehow come into being, even in a world in which up to that point no nitrogen has existed (Hull 1978: 349; 1984: 22).

In contrast, a species can only exist at time \(t_n\) if either it or a parent species existed at \(t_{n-1}\) and there was some relationship of spatial contiguity between component individuals of the species at \(t_n\) and the individuals belonging to either the same species or the parent species at \(t_{n-1}\). This is because of the essential role of the causal relationship of heredity. Heredity generates both the coherence across a population requisite for the existence of a species and the variability of predominant traits within the population, without which a species would not evolve.

For this reason, the species Homo sapiens , like every other species taxon, must meet a historical or genealogical condition. (For pluralistic objections to even this condition, see Kitcher 1984: 320ff.; Dupré 1993: 49f.) This condition is best expressed as a segment of a population-level phylogenetic tree, where such trees represent ancestor-descendent series (Hull 1978: 349; de Queiroz 1999: 50ff.; 2005). Species, as the point is often put, are historical entities, rather than kinds or classes (Hull 1978: 338ff.; 1984: 19). The fact that species are not only temporally, but also spatially restricted has also led to the stronger claim that they are individuals (Ghiselin 1974; 1997: 14ff.; Hull 1978: 338). If this is correct, then organisms are not members, but parts of species taxa. Independently of whether this claim is true for all biological species, Homo sapiens is a good candidate for a species that belongs to the category individual . This is because the species is characterised not only by spatiotemporal continuity, but also by causal processes that account for the coherence between its component parts. These processes plausibly include not only interbreeding, but also conspecific recognition and particular forms of communication (Richards 2010: 158ff., 218).

Importantly, the genealogical condition is only a necessary condition, as genealogy unites all the segments of one lineage. The segment of the phylogenetic tree that represents some species taxon begins with a node that represents a lineage-splitting or speciation event. Determining that node requires attention to general speciation theory, which has proposed various competing criteria (Dupré 1993: 48f.; Okasha 2002: 201; Coyne & Orr 2004). In the case of Homo sapiens , it requires attention to the specifics of the human case, which are also controversial (see Crow 2003; Cela-Conde & Ayala 2017: 11ff.). The end point of the segment is marked either by some further speciation event or, as may seem likely in the case of Homo sapiens , by the destruction of the metapopulation. Only when the temporal boundaries of the segment have become determinate would it be possible to adduce sufficient conditions for the existence of such a historical entity. Hence, if “human nature” is understood to pick out the necessary and sufficient conditions that individuate the species taxon Homo sapiens , its content is not only controversial, but epistemically unavailable to us.

If we take such a view of the individuating conditions for the species Homo sapiens , what are the consequences for the question of which organisms belong to the species? It might appear that it leaves open the possibility that speciation has resulted in some intrinsic property or set of properties establishing the cohesion specific to the taxon and that such properties count as necessary and sufficient for belonging to it (cf. Devitt 2008: 17ff.). This appearance would be deceptive. To begin with, no intrinsic property can be necessary because of the sheer empirical improbability that all species specimens grouped together by the relevant lineage segment instantiate any such candidate property. For example, there are individuals who are missing legs, inner organs or the capacity for language, but who remain biologically human (Hull 1986: 5). Evolutionary theory clarifies why this is so: variability, secured by mechanisms such as mutation and recombination, is the key to evolution, so that, should some qualitative property happen to be universal among all extant species specimens immediately after the completion of speciation, that is no guarantee that it will continue to be so throughout the lifespan of the taxon (Hull 1984: 35; Ereshefsky 2008: 101). The common thought that there must be at least some genetic property common to all human organisms is also false (R. Wilson 1999a: 190; Sterelny & Griffiths 1999: 7; Okasha 2002: 196f.): phenotypical properties that are shared in a population are frequently co-instantiated as a result of the complex interaction of differing gene-regulatory networks. Conversely, the same network can under different circumstances lead to differing phenotypical consequences (Walsh 2006: 437ff.). Even if it should turn out that every human organism instantiated some property, this would be a contingent, rather than a necessary fact (Sober 1980: 354; Hull 1986: 3).

Moreover, the chances of any such universal property also being sufficient are vanishingly small, as the sharing of properties by specimens of other species can result from various mechanisms, in particular from the inheritance of common genes in related species and from parallel evolution. This doesn’t entail that there may be no intrinsic properties that are sufficient belonging to the species. There are fairly good candidates for such properties, if we compare humans with other terrestrial organisms. Language use and a self-understanding as moral agents come to mind. However, whether non-terrestrial entities might possess such properties is an open question. And decisively, they are obviously hopeless as necessary conditions (cf. Samuels 2012: 9).

This leaves only the possibility that the conditions for belonging to the species are, like the individuating conditions for the species taxon, relational. Lineage-based individuation of a taxon depends on its component organisms being spatially and temporally situated in such a way that the causal processes necessary for the inheritance of traits can take place. In the human case, the key processes are those of sexual reproduction. Therefore, being an organism that belongs to the species Homo sapiens is a matter of being connected reproductively to organisms situated unequivocally on the relevant lineage segment. In other words, the key necessary condition is having been sexually reproduced by specimens of the species (Kronfeldner 2018: 100). Hull suggests that the causal condition may be disjunctive, as it could also be fulfilled by a synthetic entity created by scientists that produces offspring with humans who have been generated in the standard manner (Hull 1978: 349). Provided that the species is not in the throes of speciation, such direct descent or integration into the reproductive community, i.e., participation in the “complex network […] of mating and reproduction” (Hull 1986: 4), will also be sufficient.

The lack of a “human essence” in the sense of intrinsic necessary and sufficient conditions for belonging to the species taxon Homo sapiens , has led a number of philosophers to deny that there is any such thing as human nature (Hull 1984: 19; 1986; Ghiselin 1997: 1; de Sousa 2000). As this negative claim concerns properties intrinsic both to relevant organisms and to the taxon, it is equally directed at the “nature” of the organisms as species specimens and at that of the species taxon itself. An alternative consists in retracting the condition that a classificatory essence must be intrinsic, a move which allows talk of a historical or relational essence and a corresponding relational conception of taxonomic human nature (Okasha 2002: 202).

Which of these ways of responding to the challenge from evolutionary theory appears best is likely to depend on how one takes it that the classificatory issues relate to the other matters at stake in the original human nature package. These concern the explanatory and normative questions raised by TP1–TP4. We turn to these in the following three sections of this article.

An exclusively genealogical conception of human nature is clearly not well placed to fulfil an explanatory role comparable to that envisaged in the traditional package. What might have an explanatory function are the properties of the entities from which the taxon or its specimens are descended. Human nature, genealogically understood, might serve as the conduit for explanations in terms of such properties, but will not itself explain anything. After all, integration in a network of sexual reproduction will be partly definitive of the specimens of all sexual species, whilst what is to be explained will vary enormously across taxa.

This lack of fit between classificatory and explanatory roles confronts us with a number of further theoretical possibilities. For example, one might see this incompatibility as strengthening the worries of eliminativists such as Ghiselin and Hull: even if the subtraction of intrinsicality were not on its own sufficient to justify abandoning talk of human nature, its conjunction with a lack of explanatory power, one might think, certainly is (Dupré 2003: 109f.; Lewens 2012: 473). Or one might argue that it is the classificatory ambitions associated with talk of human nature that should be abandoned. Once this is done, one might hope that certain sets of intrinsic properties can be distinguished that figure decisively in explanations and that can still justifiably be labelled “human nature” (Roughley 2011: 15; Godfrey-Smith 2014: 140).

Taking this second line in turn raises two questions: first, in what sense are the properties thus picked out specifically “human”, if they are neither universal among, nor unique to species specimens? Second, in what sense are the properties “natural”? Naturalness as independence from the effects of human intentional action is a key feature of the original package (TP1). Whether some such conception can be coherently applied to humans is a challenge for any non-classificatory account.

3. Characteristic Human Properties

The answer given by TP2 to the first question was in terms of the fully developed human form, where “form” does not refer solely to observable physical or behavioural characteristics, but also includes psychological features. This answer entails two claims: first, that there is one single such “form”, i.e., property or set of properties, that figures in explanations that range across individual human organisms. It also entails that there is a point in human development that counts as “full”, that is, as development’s goal or “telos”. These claims go hand in hand with the assumption that there is a distinction to be drawn between normal and abnormal adult specimens of the species. There is, common sense tells us, a sense in which normal adult humans have two legs, two eyes, one heart and two kidneys at specific locations in the body; they also have various dispositions, for instance, to feel pain and to feel emotions, and a set of capacities, such as for perception and for reasoning. And these, so it seems, may be missing, or under- or overdeveloped in abnormal specimens.

Sober has influentially described accounts that work with such teleological assumptions as adhering to an Aristotelian “Natural State Model” (Sober 1980: 353ff.). Such accounts work with a distinction that has no place in evolutionary biology, according to which variation of properties across populations is the key to evolution. Hence, no particular end states of organisms are privileged as “natural” or “normal” (Hull 1986: 7ff.). So any account that privileges particular morphological, behavioural or psychological human features has to provide good reasons that are both non-evolutionary and yet compatible with the evolutionary account of species. Because of the way that the notion of the normal is frequently employed to exclude and oppress, those reasons should be particularly good (Silvers 1998; Dupré 2003: 119ff.; Richter 2011: 43ff.; Kronfeldner 2018: 15ff.).

The kinds of reasons that may be advanced could either be internal to, or independent of the biological sciences. If the former, then various theoretical options may seem viable. The first grounds in the claim that, although species are not natural kinds and are thus unsuited to figuring in laws of nature (Hull 1987: 171), they do support descriptions with a significant degree of generality, some of which may be important (Hull 1984: 19). A theory of human nature developed on this basis should explain the kind of importance on the basis of which particular properties are emphasised. The second theoretical option is pluralism about the metaphysics of species: in spite of the fairly broad consensus that species are defined as units of evolution, the pluralist can deny the primacy of evolutionary dynamics, arguing that other epistemic aims allow the ecologist, the systematist or the ethologist to work with an equally legitimate concept of species that is not, or not exclusively genealogical (cf. Hull 1984: 36; Kitcher 1986: 320ff.; Hull 1987: 178–81; Dupré 1993: 43f.). The third option involves a relaxation of the concept of natural kinds, such that it no longer entails the instantiation of intrinsic, necessary, sufficient and spatiotemporally unrestricted properties, but is nevertheless able to support causal explanations. Such accounts aim to reunite taxonomic and explanatory criteria, thus allowing species taxa to count as natural kinds after all (Boyd 1999a; R. Wilson, Barker, & Brigandt 2007: 196ff.). Where, finally , the reasons advanced for privileging certain properties are independent of biology, these tend to concern features of humans’—“our”—self-understanding as participants in, rather than observers of, a particular form of life. These are likely to be connected to normative considerations. Here again, it seems that a special explanation will be required for why these privileged properties should be grouped under the rubric “human nature”.

The accounts to be described in the next subsection (3.2) of this entry are examples of the first strategy. Section 4 includes discussion of the relaxed natural kinds strategy. Section 5 focuses on accounts of human nature developed from a participant perspective and also notes the support that the pluralist metaphysical strategy might be taken to provide.

Begin, then, with the idea that to provide an account of “human nature” is to circumscribe a set of generalisations concerning humans. An approach of this sort sees the properties thus itemised as specifically “human” in as far as they are common among species specimens. So the privilege accorded to these properties is purely statistical and “normal” means statistically normal. Note that taking the set of statistically normal properties of humans as a non-teleological replacement for the fully developed human form retains from the original package the possibility of labelling as “human nature” either those properties themselves (TP3) or their developmental cause (TP2). Either approach avoids the classificatory worries dealt with in section 2 : it presupposes that those organisms whose properties are relevant are already distinguished as such specimens. What is to be explained is, then, the ways humans generally, though not universally, are. And among these ways are ways they may share with most specimens of some other species, in particular those that belong to the same order (primates) and the same class (mammals).

One should be clear what follows from this interpretation of “human”. The organisms among whom statistical frequency is sought range over those generated after speciation around 150,000 years ago to those that will exist immediately prior to the species’ extinction. On the one hand, because of the variability intrinsic to species, we are in the dark as to the properties that may or may not characterise those organisms that will turn out to be the last of the taxon. On the other hand, the time lag of around 100,000 years between the first anatomically modern humans and the general onset of behavioural modernity around the beginning of the Upper Palaeolithic means that there are likely to be many widespread psychological properties of contemporary humans that were not possessed by the majority of the species’ specimens during two thirds of the species’ history. This is true even if the practices seen as the signatures of behavioural modernity (see §1.1 ) developed sporadically, disappeared and reappeared at far removed points of time and space over tens of thousands of years before 50,000 ka (McBrearty & Brooks 2000; Sterelny 2011).

According to several authors (Machery 2008; 2018; Samuels 2012; Ramsey 2013), the expression “human nature” should be used to group properties that are the focus of much current behavioural, psychological and social science. However, as the cognitive and psychological sciences are generally interested in present-day humans, there is a mismatch between scientific focus and a grouping criterion that takes in all the properties generally or typically instantiated by specimens of the entire taxon. For this reason, the expression “human nature” is likely to refer to properties of an even more temporally restricted set of organisms belonging to the species. That restriction can be thought of in indexical terms, i.e., as a restriction to contemporary humans. However, some authors claim explicitly that their accounts entail that human nature can change (Ramsey 2013: 992; Machery 2018: 20). Human nature would then be the object of temporally indexed investigations, as is, for example, the weight of individual humans in everyday contexts. (Without temporal specification, there is no determinate answer to a question such as “How much did David Hume weigh?”) An example of Machery’s is dark skin colour. This characteristic, he claims, ceased to be a feature of human nature thus understood 7,000 years ago, if that was when skin pigmentation became polymorphic. The example indicates that the temporal range may be extremely narrow from an evolutionary point of view.

Such accounts are both compatible with evolutionary theory and coherent. However, in as far as they are mere summary or list conceptions, it is unclear what their epistemic value might be. They will tend to accord with everyday common sense, for which “human nature” may in a fairly low-key sense simply be the properties that (contemporary) humans generally tend to manifest (Roughley 2011: 16). They will also conform to one level of the expression’s use in Hume’s Treatise of Human Nature (1739–40), which, in an attempt to provide a human “mental geography” (1748 [1970: 13]), lists a whole series of features, such as prejudice (1739–40, I,iii,13), selfishness (III,ii,5), a tendency to temporal discounting (III,ii,7) and an addiction to general rules (III,ii,9).

Accounts of this kind have been seen as similar in content to field guides for other animals (Machery 2008: 323; Godfrey-Smith 2014: 139). As Hull points out, within a restricted ecological context and a short period of evolutionary time, the ascription of readily observable morphological or behavioural characteristics to species specimens is a straightforward and unproblematic enterprise (Hull 1987: 175). However, the analogy is fairly unhelpful, as the primary function of assertions in field guides is to provide a heuristics for amateur classification. In contrast, a list conception of the statistically normal properties of contemporary humans presupposes identification of the organisms in question as humans. Moreover, such accounts certainly do not entail easy epistemic access to the properties in question, which may only be experimentally discovered. Nevertheless, there remains something correct about the analogy, as such accounts are a collection of assertions linked only by the fact that they are about the same group of organisms (Sterelny 2018: 123).

More sophisticated nature documentaries may summarise causal features of the lives of animals belonging to specific species. An analogous conception of human nature has also been proposed, according to which human nature is a set of pervasive and robust causal nexuses amongst humans. The list that picks out this set would specify causal connections between antecedent properties, such as having been exposed to benzene or subject to abuse as a child, and consequent properties, such as developing cancer or being aggressive towards one’s own children (Ramsey 2013: 988ff.). Human nature thus understood would have an explanatory component, a component internal to each item on the list. Human nature itself would, however, not be explanatory, but rather the label for a list of highly diverse causal connections.

An alternative way to integrate an explanatory component in a statistical normality account involves picking out that set of statistically common properties that have a purely evolutionary explanation (Machery 2008; 2018). This reinterpretation of the concept of naturalness that featured in the original package (TP1) involves a contrast with social learning. Processes grouped together under this latter description are taken to be alternative explanations to those provided by evolution. However, learning plays a central role, not only in the development of individual humans, but also in the iterated interaction of entire populations with environments structured and restructured through such interaction (Stotz 2010: 488ff.; Sterelny 2012: 23ff.). Hence, the proposal raises serious epistemic questions as to how the distinction is precisely to be drawn and operationalised. (For discussion, see Prinz 2012; Lewens 2012: 464ff.; Ramsey 2013: 985; Machery 2018: 15ff.; Sterelny 2018: 116; Kronfeldner 2018: 147ff.).

4. Explanatory Human Properties

The replacement of the concept of a fully developed form with a statistical notion yields a deflationary account of human nature with, at most, restricted explanatory import. The correlative, explanatory notion in the original package, that of the fully developed form’s blueprint (TP2), has to some authors seemed worth reframing in terms made possible by advances in modern biology, particularly in genetics.

Clearly, there must be explanations of why humans generally walk on two legs, speak and plan many of their actions in advance. Genealogical, or what have been called “ultimate” (Mayr) or “historical” (Kitcher) explanations can advert to the accumulation of coherence among entrenched, stable properties along a lineage. These may well have resulted from selection pressures shared by the relevant organisms (cf. Wimsatt 2003; Lewens 2009). The fact that there are exceptions to any generalisations concerning contemporary humans does not entail that there is no need for explanations of such exception-allowing generalisations. Plausibly, these general, though not universal truths will have “structural explanations”, that is, explanations in terms of underlying structures or mechanisms (Kitcher 1986: 320; Devitt 2008: 353). These structures, so seems, might to a significant degree be inscribed in humans’ DNA.

The precise details of rapidly developing empirical science will improve our understanding of the extent to which there is a determinate relationship between contemporary humans’ genome and their physical, psychological and behavioural properties. There is, however, little plausibility that the blueprint metaphor might be applicable to the way DNA is transcribed, translated and interacts with its cellular environment. Such interaction is itself subject to influence by the organism’s external environment, including its social environment (Dupré 2001: 29ff.; 2003: 111ff.; Griffiths 2011: 326; Prinz 2012: 17ff.; Griffiths & Tabery 2013: 71ff.; Griffiths & Stotz 2013: 98ff., 143ff.). For example, the feature of contemporary human life for which there must according to Aristotle be some kind of blueprint, viz. rational agency, is, as Sterelny has argued, so strongly dependent on social scaffolding that any claim to the effect that human rationality is somehow genetically programmed ignores the causal contributions of manifestly indispensable environmental factors (Sterelny 2018: 120).

Nevertheless, humans do generally develop a specific set of physiological features, such as two lungs, one stomach, one pancreas and two eyes. Moreover, having such a bodily architecture is, according to the evidence from genetics, to a significant extent the result of developmental programmes that ground in gene regulatory networks (GRNs). These are stretches of non-coding DNA that regulate gene transcription. GRNs are modular, more or less strongly entrenched structures. The most highly conserved of these tend to be the phylogenetically most archaic (Carroll 2000; Walsh 2006: 436ff.; Willmore 2012: 227ff.). The GRNs responsible for basic physiological features may be taken, in a fairly innocuous sense, to belong to an evolved human nature.

Importantly, purely morphological features have generally not been the explananda of accounts that have gone under the rubric “human nature”. What has frequently motivated explanatory accounts thus labelled is the search for underlying structures responsible for generally shared psychological features. “Evolutionary Psychologists” have built a research programme around the claim that humans share a psychological architecture that parallels that of their physiology. This, they believe, consists of a structured set of psychological “organs” or modules (Tooby & Cosmides 1990: 29f.; 1992: 38, 113). This architecture is, they claim, in turn the product of developmental programmes inscribed in humans’ DNA (1992: 45). Such generally distributed developmental programmes they label “human nature” (1990: 23).

This conception raises the question of how analogous the characteristic physical and psychological “architectures” are. For one thing, the physical properties that tend to appear in such lists are far more coarse-grained than the candidates for shared psychological properties (D. Wilson 1994: 224ff.): the claim is not just that humans tend to have perceptual, desiderative, doxastic and emotional capacities, but that the mental states that realise these capacities tend to have contents of specific types. Perhaps an architecture of the former kind—of a formal psychology—is a plausible, if relatively unexciting candidate for the mental side of what an evolved human nature should explain. Either way, any such conception needs to adduce criteria for the individuation of such “mental organs” (D. Wilson 1994: 233). Relatedly, if the most strongly entrenched developmental programmes are the most archaic, it follows that, although these will be species-typical, they will not be species-specific. Programmes for the development of body parts have been identified for higher taxa, rather than for species.

A further issue that dogs any such attempts to explicate the “human” dimension of human nature in terms of developmental programmes inscribed in human DNA concerns Evolutionary Psychologists’ assertion that the programmes are the same in every specimen of the species. This assertion goes hand in hand with the claim that what is explained by such programmes is a deep psychological structure that is common to almost all humans and underlies the surface diversity of behavioural and psychological phenomena (Tooby & Cosmides 1990: 23f.). For Evolutionary Psychologists, the (near-)universality of both developmental programmes and deep psychological structure has an ultimate explanation in evolutionary processes that mark their products as natural in the sense of TP1. Both, they claim, are adaptations. These are features that were selected for because their possession in the past conferred a fitness advantage on their possessors. Evolutionary Psychologists conceive that advantage as conferred by the fulfilment of some specific function. They summarise selection for that function as “design”, which they take to have operated equally on all species specimens since the Pleistocene. This move reintroduces the teleological idea of a fully developed form beyond mere statistical normality (TP3).

This move has been extensively criticised. First, selection pressures operate at the level of groups and hence need not lead to the same structures in all a group’s members (D. Wilson 1994: 227ff.; Griffiths 2011: 325; Sterelny 2018: 120). Second, other evolutionary mechanisms than natural selection might be explanatorily decisive. Genetic drift or mutation and recombination might, for example, also confer “naturalness” in the sense of evolutionary genesis (Buller 2000: 436). Third, as we have every reason to assume that the evolution of human psychology is ongoing, evolutionary biology provides little support for the claim that particular programmes and associated traits evolved to fixity in the Pleistocene (Buller 2000: 477ff.; Downes 2010).

Perhaps, however, there might turn out to be gene control networks that do generally structure certain features of the psychological development of contemporary humans (Walsh 2006: 440ff.). The quest for such GNRs can, then, count as the search for an explanatory nature of contemporary humans, where the explanatory function thus sought is divorced from any classificatory role.

There has, however, been a move in general philosophy of science that, if acceptable, would transform the relationship between the taxonomic and explanatory features of species. This move was influentially initiated by Richard Boyd (1999a). It begins with the claim that the attempt to define natural kinds in terms of spatiotemporally unrestricted, intrinsic, necessary and sufficient conditions is a hangover from empiricism that should be abandoned by realist metaphysics. Instead, natural kinds should be understood as kinds that support induction and explanation, where generalisations at work in such processes need not be exceptionless. Thus understood, essences of natural kinds, i.e., their “natures”, need be neither intrinsic nor be possessed by all and only members of the kinds. Instead, essences consist of property clusters integrated by stabilising mechanisms (“homeostatic property clusters”, HPCs). These are networks of causal relations such that the presence of certain properties tends to generate or uphold others and the workings of underlying mechanisms contribute to the same effect. Boyd names storms, galaxies and capitalism as plausible examples (Boyd 1999b: 82ff.). However, he takes species to be the paradigmatic HPC kinds. According to this view, the genealogical character of a species’ nature does not undermine its causal role. Rather, it helps to explain the specific way in which the properties cohere that make up the taxon’s essence. Moreover, these can include extrinsic properties, for example, properties of constructed niches (Boyd 1991: 142, 1999a: 164ff.; Griffiths 1999: 219ff.; R. Wilson et al. 2007: 202ff.).

Whether such an account can indeed adequately explain taxonomic practice for species taxa is a question that can be left open here (see Ereshefsky & Matthen 2005: 16ff.). By its own lights the account does not identify conditions for belonging to a species such as Homo sapiens (Samuels 2012: 25f.). Whether it enables the identification of factors that play the explanatory roles that the term “human nature” might be supposed to pick out is perhaps the most interesting question. Two ways in which an account of human nature might be developed from such a starting point have been sketched.

According to Richard Samuels’ proposal, human nature should be understood as the empirically discoverable proximal mechanisms responsible for psychological development and for the manifestation of psychological capacities. These will include physiological mechanisms, such as the development of the neural tube, as well as environmentally scaffolded learning procedures; they will also include the various modular systems distinguished by cognitive science, such as visual processing and memory systems (Samuels 2012: 22ff.). Like mere list conceptions (cf. §3.2 ), such an account has a precedent in Hume, for whom human nature also includes causal “principles” that structure operations of the human mind (1739–40, Intro.), for example, the mechanisms of sympathy (III,iii,1; II,ii,6). Hume, however, thought of the relevant causal principles as intrinsic.

A second proposal, advanced by Paul Griffiths and Karola Stotz, explicitly suggests taking explanandum and explanans to be picked out by different uses of the expression "human nature". In both cases, the “nature” in question is that of the taxon, not of individual organisms. The former use simply refers to “what human beings are like”, where “human beings” means all species specimens. Importantly, this characterisation does not aim at shared characteristics, but is open for polymorphisms both across a population and across life stages of individual organisms. The causal conception of human nature, what explains this spectrum of similarity and difference in life histories, is equated by Griffiths and Stotz with the organism-environment system that supports human development. It thus includes all the genetic, epigenetic and environmental resources responsible for varying human life cycles (Griffiths 2011: 319; Stotz & Griffiths 2018, 66f.). It follows that explanatory human nature at one point in time can be radically different from human nature at some other point in time.

Griffiths and Stotz are clear that this account diverges significantly from traditional accounts, as it rejects assumptions that human development has a goal, that human nature is possessed by all and only specimens of the species and that it consists of intrinsic properties. They see these assumptions as features of the folk biology of human nature that is as scientifically relevant as are folk conceptions of heat for its scientific understanding (Stotz 2010: 488; Griffiths 2011: 319ff.; Stotz & Griffiths 2018: 60ff.). This raises the question as to whether such a developmental systems account should not simply advocate abandoning the term, as is suggested by Sterelny (2018) on the basis of closely related considerations. A reason for not doing so might lie in the fact that, as talk of “human nature” is often practised with normative intent or at least with normative consequences (Stotz & Griffiths 2018: 71f.), use of the term to pick out the real, complex explanatory factors at work might help to counter those normative uses that employ false, folk biological assumptions.

Explanatory accounts that emphasise developmental plasticity in the products of human DNA, in the neural architecture of the brain and in the human mind tend to reject the assumption that explanations of what humans are like should focus on intrinsic features. It should, however, be noted that such accounts can be interpreted as assigning the feature of heightened plasticity the key role in such explanations (cf. Montagu 1956: 79). Accounts that make plasticity causally central also raise the question as to whether there are not biological features that in turn explain it and should therefore be assigned a more central status in a theory of explanatory human nature.

A prime candidate for this role is what the zoologist Adolf Portmann labelled human “secondary altriciality”, a unique constellation of features of the human neonate relative to other primates: human neonates are, in their helplessness and possession of a relatively undeveloped brain, neurologically and behaviourally altricial, that is, in need of care. However they are also born with open and fully functioning sense organs, otherwise a mark of precocial species, in which neonates are able to fend for themselves (Portmann 1951: 44ff.). The facts that the human neonate brain is less than 30% of the size of the adult brain and that brain development after birth continues at the fetal rate for the first year (Walker & Ruff 1993, 227) led the anthropologist Ashley Montagu to talk of “exterogestation” (Montagu 1961: 156). With these features in mind, Portmann characterised the care structures required by prolonged infant helplessness as the “social uterus” (Portmann 1967: 330). Finally, the fact that the rapid development of the infant brain takes place during a time in which the infant’s sense organs are open and functioning places an adaptive premium on learning that is unparalleled among organisms (Gould 1977: 401; cf. Stotz & Griffiths 2018: 70).

Of course, these features are themselves contingent products of evolution that could be outlived by the species. Gould sees them as components of a general retardation of development that has characterised human evolution (Gould 1977: 365ff.), where “human” should be seen as referring to the clade—all the descendants of a common ancestor—rather than to the species. Anthropologists estimate that secondary altriciality characterised the lineage as from Homo erectus 1.5 million years ago (Rosenberg & Trevathan 1995: 167). We are, then, dealing with a set of deeply entrenched features, features that were in place long before behavioural modernity.

It is conceivable that the advent of secondary altriciality was a key transformation in generating the radical plasticity of human development beginning with early hominins. However, as Sterelny points out, there are serious difficulties with isolating any particular game changer. Secondary altriciality, or the plasticity that may in part be explained by it, would thus seem to fall victim to the same verdict as the game changers named by the traditional human nature slogans. However, maybe it is more plausible to think in terms of a matrix of traits: perhaps a game-changing constellation of properties present in the population after the split from pan can be shown to have generated forms of niche construction that fed back into and modified the original traits. These modifications may in turn have had further psychological and behavioural consequences in steps that plausibly brought selective advantages (Sterelny 2018: 115).

5. Human Nature, the Participant Perspective and Morality

In such a culture-mind coevolutionary account, there may be a place for the referents of some of the traditional philosophical slogans intended to pin down “the human essence“ or “human nature”—reason, linguistic capacity ( “ the speaking animal”, Herder 1772 [2008: 97]), a more general symbolic capacity ( animal symbolicum , Cassirer 1944: 44), freedom of the will (Pico della Mirandola 1486 [1965: 5]; Sartre 1946 [2007: 29, 47]), a specific, “political” form of sociality, or a unique type of moral motivation (Hutcheson 1730: §15). These are likely, at best, to be the (still evolving) products in contemporary humans of processes set in motion by a trait constellation that includes proto-versions of (some of) these capacities. Such a view may also be compatible with an account of “what contemporary humans are like” that abstracts from the evolutionary time scale of eons and focuses instead on the present (cf. Dupré 1993: 43), whilst neither merely cataloguing widely distributed traits ( §3.2 ) nor attempting explanations in terms of the human genome ( §4.1 ). The traditional slogans appear to be attempts to summarise some such accounts. It seems clear, though, that their aims are significantly different from those of the biologically, or otherwise scientifically orientated positions thus far surveyed.

Two features of such accounts are worth emphasising, both of which we already encountered in Aristotle’s contribution to the original package. The first involves a shift in perspective from that of the scientific observer to that of a participant in a contemporary human life form. Whereas the human—or non-human—biologist may ask what modern humans are like, just as they may ask what bonobos are like, the question that traditional philosophical accounts of human nature are plausibly attempting to answer is what it is like to live one’s life as a contemporary human. This question is likely to provoke the counter-question as to whether there is anything that it is like to live simply as a contemporary human, rather than as a human-in-a-specific-historical-and-cultural context (Habermas 1958: 32; Geertz 1973: 52f.; Dupré 2003: 110f.). For the traditional sloganeers, the answer is clearly affirmative. The second feature of such accounts is that they tend to take it that reference to the capacities named in the traditional slogans is in some sense normatively , in particular, ethically significant .

The first claim of such accounts, then, is that there is some property of contemporary humans that is in some way descriptively or causally central to participating in their form of life. The second is that such participation involves subjection to normative standards rooted in the possession of some such property. Importantly, there is a step from the first to the second form of significance, and justification of the step requires argument. Even from a participant perspective, there is no automatic move from explanatory to normative significance.

According to an “internal”, participant account of human nature, certain capacities of contemporary, perhaps modern humans unavoidably structure the way they (we) live their (our) lives. Talk of “structuring” refers to three kinds of contributions to the matrix of capacities and dispositions that both enable and constrain the ways humans live their lives. These are contributions, first, to the specific shape other features of humans lives have and, second, to the way other such features hang together (Midgley 2000: 56ff.; Roughley 2011: 16ff.). Relatedly, they also make possible a whole new set of practices. All three relations are explanatory, although their explanatory role appears not necessarily to correspond to the role corresponding features, or earlier versions of the features, might have played in the evolutionary genealogy of contemporary human psychology. Having linguistic capacities is a prime candidate for the role of such a structural property: human perception, emotion, action planning and thought are all plausibly transformed in linguistic creatures, as are the connections between perception and belief, and the myriad relationships between thought and behaviour, connections exploited and deepened in a rich set of practices unavailable to non-linguistic animals. Similar things could be claimed for other properties named by the traditional slogans.

In contrast to the ways in which such capacities have frequently been referred to in the slogan mode, particularly to the pathos that has tended to accompany it, it seems highly implausible that any one such property will stand alone as structurally significant. It is more likely that we should be picking out a constellation of properties, a constellation that may well include properties variants of which are possessed by other animals. Other properties, including capacities that may be specific to contemporary humans, such as humour, may be less plausible candidates for a structural role.

Note that the fact that such accounts aim to answer a question asked from the participant perspective does not rule out that the features in question may be illuminated in their role for human self-understanding by data from empirical science. On the contrary, it seems highly likely that disciplines such as developmental and comparative psychology, and neuroscience will contribute significantly to an understanding of the possibilities and constraints inherent in the relevant capacities and in the way they interact.

5.2. Human Nature and the Human ergon

The paradigmatic strategy for deriving ethical consequences from claims about structural features of the human life form is the Platonic and Aristotelian ergon or function argument. The first premise of Aristotle’s version ( Nicomachean Ethics 1097b–1098a) connects function and goodness: if the characteristic function of an entity of a type X is to φ, then a good entity of type X is one that φs well. Aristotle confers plausibility on the claim by using examples such as social roles and bodily organs. If the function of an eye as an exemplar of its kind is to enable seeing, then a good eye is one that enables its bearer to see well. The second premise of the argument is a claim we encountered in section 1.4 of this entry, a claim we can now see as predicating a structural property of human life, the exercise of reason. According to this claim, the function or end of individual humans as humans is, depending on interpretation (Nussbaum 1995: 113ff.), either the exercise of reason or life according to reason. If this is correct, it follows that a good human being is one whose life centrally involves the exercise of, or life in accordance with, reason.

In the light of the discussion so far, it ought to be clear that, as it stands, the second premise of this argument is incompatible with the evolutionary biology of species. It asserts that the exercise of reason is not only the key structural property of human life, but also the realization of the fully developed human form. No sense can be made of this latter notion in evolutionary terms. Nevertheless, a series of prominent contemporary ethicists—Alasdair MacIntyre (1999), Rosalind Hursthouse (1999), Philippa Foot (2001) and Martha Nussbaum (2006)—have all made variants of the ergon argument central to their ethical theories. As each of these authors advance some version of the second premise, it is instructive to examine the ways in which they aim to avoid the challenge from evolutionary biology.

Before doing so, it is first worth noting that any ethical theory or theory of value is engaged in an enterprise that has no clear place in an evolutionary analysis. If we want to know what goodness is or what “good” means, evolutionary theory is not the obvious place to look. This is particularly clear in view of the fact that evolutionary theory operates at the level of populations (Sober 1980: 370; Walsh 2006: 434), whereas ethical theory operates, at least primarily, at the level of individual agents. However, the specific conflict between evolutionary biology and neo-Aristotelian ethics results from the latter’s constructive use of the concept of species and, in particular, of a teleological conception of a fully developed form of individual members of the species “ qua members of [the] species” (MacIntyre 1999: 64, 71; cf. Thompson 2008: 29; Foot 2001: 27). The characterisation of achieving that form as fulfilling a “function”, which helps the analogy with bodily organs and social roles, is frequently replaced in contemporary discussions by talk of “flourishing” (Aristotle’s eudaimonia ). Such talk more naturally suggests comparisons with the lives of other organisms (although Aristotle himself excludes other animals from eudaimonia ; cf. Nicomachean Ethics 1009b). The concept of flourishing in turn picks out biological—etymologically: botanical—processes, but again not of a sort that play a role in evolutionary theory. It also seems primarily predicated of individual organisms. It may play a role in ecology; it is, however, most clearly at home in practical applications of biological knowledge, as in horticulture. In this respect, it is comparable to the concept of health.

Neo-Aristotelians claim that to describe an organism, whether a plant or a non-human or human animal, as flourishing is to measure it against a standard that is specific to the species to which it belongs. To do so is to evaluate it as a more or less good “specimen of its species (or sub-species)” (Hursthouse 1999: 198). The key move is then to claim that moral evaluation is, “quite seriously” (Foot 2001: 16), evaluation of the same sort: just as a non-defective animal or plant exemplifies flourishing within the relevant species’ life form, someone who is morally good is someone who exemplifies human flourishing, i.e., the fully developed form of the species. This metaethical claim has provoked the worry as to whether such attributions to other organisms are really anything more than classifications, or at most evaluations of “stretched and deflated” kinds that are missing the key feature of authority that we require for genuine normativity (Lenman 2005: 46ff.).

Independently of questions concerning their theory of value, ethical Neo-Aristotelians need to respond to the question of how reference to a fully developed form of the species can survive the challenge from evolutionary theory. Three kinds of response may appear promising.

The first adverts to the plurality of forms of biological science, claiming that there are life sciences, such as physiology, botany, zoology and ethology in the context of which such evaluations have a place (Hursthouse 1999: 202; 2012: 172; MacIntyre 1999: 65). And if ethology can legitimately attribute not only characteristic features, but also defects or flourishing to species members, in spite of species not being natural kinds, then there is little reason why ethics shouldn’t do so too. This strategy might ground in one of the moves sketched in section 3.1 of this entry. It might be argued, with Kitcher and Dupré, that such attributions are legitimate in other branches of biological science because there is a plurality of species concepts, indeed of kinds of species, where these are relative to epistemic interests. Or the claim might simply rest on a difference in what is taken to be the relevant time frame, where temporal relevance is indexed relative to the present. In ethics we are, it might be claimed, interested in humans as they are “at the moment and for a few millennia back and for maybe not much longer in the future” (Hursthouse 2012: 171).

This move amounts to the concession that talk of “the human species” is not to be understood literally. Whether this concession undermines the ethical theories that use the term is perhaps unclear. It leaves open the possibility that, as human nature may change significantly, there may be significant changes in what it means for humans to flourish and therefore in what is ethically required. This might be seen as a virtue, rather than a vice of the view.

A second response to the challenge from evolutionary biology aims to draw metaphysical consequences from epistemic or semantic claims. Michael Thompson has argued that what he calls alternatively “the human life form” and “the human species” is an a priori category. Thompson substantiates this claim by examining forms of discourse touched on in section 3.2 , forms of discourse that are generally taken to be of mere heuristic importance for amateur practices of identification, viz. field guides or animal documentaries. Statements such as “The domestic cat has four legs, two eyes, two ears and guts in its belly”, are, Thompson claims, instances of an important kind of predication that is neither tensed nor quantifiable. He calls these “natural historical descriptions” or “Aristotelian categoricals” (Thompson 2008: 64ff.). Such generic claims are not, he argues, made false where what is predicated is less than universal, or even statistically rare. Decisively, according to Thompson, our access to the notion of the human life form is non-empirical. It is, he claims, a presupposition of understanding ourselves from the first-person perspective as breathing, eating or feeling pain (Thompson 2004: 66ff.). Thus understood, the concept is independent of biology and therefore, if coherent, immune to problems raised by the Darwinian challenge.

Like Foot and Hursthouse, Thompson thinks that his Aristotelian categoricals allow inferences to specific judgments that members of species are defective (Thompson 2004: 54ff.; 2008: 80). He admits that such judgments in the case of the human life form are likely to be fraught with difficulties, but nevertheless believes that judgments of (non-)defective realization of a life form are the model for ethical evaluation (Thompson 2004: 30, 81f.). It may seem unclear how this might be the case in view of the fact that access to the human life form is supposed to be given as a presupposition of using the concept of “I”. Another worry is that the everyday understanding on which Thompson draws may be nothing other than a branch of folk biology. The folk tendency to ascribe teleological essences to species, as to “races” and genders, is no indication of the reality of such essences (Lewens 2012: 469f.; Stotz & Griffiths 2018: 60ff.; cf. Pellegrin 1982 [1986: 16ff., 120] and Charles 2000: 343ff., 368, on Aristotle’s own orientation to the usage of “the people”).

A final response to evolutionary biologists’ worries aims equally to distinguish the Neo-Aristotelian account of human nature from that of the sciences. However, it does so not by introducing a special metaphysics of “life forms”, but by explicitly constructing an ethical concept of human nature. Martha Nussbaum argues that the notion of human nature in play in what she calls “Aristotelian essentialism” is, as she puts it, “internal and evaluative”. It is a hermeneutic product of “human” self-understanding, constructed from within our best ethical outlook: “an ethical theory of human nature”, she claims,

should force us to answer for ourselves, on the basis of our very own ethical judgment, the question which beings are fully human ones. (Nussbaum 1995: 121f.; cf. Nussbaum 1992: 212ff.; 2006: 181ff.; McDowell 1980 [1998: 18ff.]; Hursthouse 1999: 229; 2012: 174f.)

There can be no question here of moving from a biological “is” to an ethical “ought”; rather, which features are taken to belong to human nature is itself seen as the result of ethical deliberation. Such a conception maintains the claim that the key ethical standard is that of human flourishing. However, it is clear that what counts as flourishing can only be specified on the basis of ethical deliberation, understood as striving for reflective equilibrium (Nussbaum 2006: 352ff.). In view of such a methodological proposal, there is a serious question as to what work is precisely done by the concept of human nature.

Neo-Aristotelians vary in the extent to which they flesh out a conception of species-specific flourishing. Nussbaum draws up a comprehensive, open-ended catalogue of what she calls “the central human capacities”. These are in part picked out because of their vulnerability to undermining or support by political measures. They include both basic bodily needs and more specifically human capacities, such as for humour, play, autonomy and practical reason (Nussbaum 1992: 216ff.; 2006: 76ff.). Such a catalogue allows the setting of three thresholds, below which a human organism would not count as living a human life at all (anencephalic children, for instance), as living a fully human life or as living a good human life (Nussbaum 2006: 181). Nussbaum explicitly argues that being of human parents is insufficient for crossing the first, evaluatively set threshold. Her conception is partly intended to provide guidelines as to how societies should conceive disability and as to when it is appropriate to take political measures in order to enable agents with nonstandard physical or mental conditions to cross the second and third thresholds.

Nussbaum has been careful to insist that enabling independence, rather than providing care, should be the prime aim. Nevertheless, the structure of an account that insists on a “species norm”, below which humans lacking certain capacities count as less than fully flourishing, has prompted accusations of illiberality. According to the complaint, it disrespects the right of members of, for example, deaf communities to set the standards for their own forms of life (Glackin 2016: 320ff.).

Other accounts of species-specific flourishing have been considerably more abstract. According to Hursthouse, plants flourish when their parts and operations are well suited to the ends of individual survival and continuance of the species. In social animals, flourishing also tends to involve characteristic pleasure and freedom from pain, and a contribution to appropriate functioning of relevant social groups (Hursthouse 1999: 197ff.). The good of human character traits conducive to pursuit of these four ends is transformed, Hursthouse claims, by the addition of “rationality”. As a result, humans flourish when they do what they correctly take themselves to have reason to do—under the constraint that they do not thereby cease to foster the four ends set for other social animals (Hursthouse 1999: 222ff.). Impersonal benevolence is, for example, because of this constraint, unlikely to be a virtue. In such an ethical outlook, what particular agents have reason to do is the primary standard; it just seems to be applied under particular constraints. A key question is thus whether the content of this primary standard is really determined by the notion of species-specific flourishing.

Where Hursthouse’s account builds up to, and attempts to provide a “natural” framework for, the traditional Aristotelian ergon of reason, MacIntyre builds his account around the claim that flourishing specific to the human “species” is essentially a matter of becoming an “independent practical reasoner” (MacIntyre 1999: 67ff.). It is because of the central importance of reasoning that, although human flourishing shares certain preconditions with the flourishing, say, of dolphins, it is also vulnerable in specific ways. MacIntyre argues that particular kinds of social practices enable the development of human reasoning capacities and that, because independent practical reasoning is, paradoxically, at core cooperatively developed and structured, the general aim of human flourishing is attained by participation in networks in local communities (MacIntyre 1999: 108). “Independent practical reasoners” are “dependent rational animals”. MacIntyre’s account thus makes room on an explanatory level for the evolutionary insight that humans can only become rational in a socio-cultural context which provides scaffolding for the development and exercise of rationality ( §4 ). Normatively, however, this point is subordinated to the claim that, from the point of view of participation in the contemporary human life form, flourishing corresponds to the traditional slogan.

MacIntyre, Hursthouse and Nussbaum (Nussbaum 2006: 159f.) all aim to locate the human capacity for reasoning within a framework that encompasses other animals. Each argues that, although the capacities to recognise reasons as reasons and for deliberation on their basis transform the needs and abilities humans share with other animals, the reasons in question remain in some way dependent on humans’ embodied and social form of life. This emphasis is intended to distinguish an Aristotelian approach from other approaches for which the capacity to evaluate reasons for action as reasons and to distance oneself from ones desires is also the “central difference” between humans and other animals (Korsgaard 2006: 104; 2018: 38ff.; cf. MacIntyre 1999: 71ff.). According to Korsgaard’s Kantian interpretation of Aristotle’s ergon argument, humans cannot act without taking a normative stand on whether their desires provide them with reasons to act. This she takes to be the key structural feature of their life, which brings with it “a whole new way of functioning well or badly” (Korsgaard 2018: 48; cf. 1996: 93). In such an account, “human nature” is monistically understood as this one structural feature which is so transformative that the concept of life applicable to organisms that instantiate it is no longer that applicable to organisms that don’t. Only “humans” live their lives, because only they possess the type of intentional control over their bodily movements that grounds in evaluation of their actions and self-evaluation as agents (Korsgaard 2006: 118; 2008: 141ff.; cf. Plessner 1928 [1975: 309f.]).

We have arrived at an interpretation of the traditional slogan that cuts it off from a metaphysics with any claims to be “naturalistic”. The claim now is that the structural effect of the capacity for reasoning transforms those features of humans that they share with other animals so thoroughly that those features pale into insignificance. What is “natural” about the capacity for reasoning for humans here is its unavoidability for contemporary members of the species, at least for those without serious mental disabilities. Such assertions also tend to shade into normative claims that discount the normative status of “animal” needs in view of the normative authority of human reasoning (cf. McDowell 1996 [1998: 172f.]).

The most radical version of this thought leads to the claim encountered towards the end of section 1.4 : that talk of “human nature” involves no essential reference at all to the species Homo sapiens or to the hominin lineage. According to this view, the kind to which contemporary humans belong is a kind to which entities could also belong who have no genealogical relationship to humans. That kind is the kind of entities that act and believe in accordance with the reasons they take themselves to have. Aliens, synthetically created agents and angels are further candidates for membership in the kind, which would, unlike biological taxa, be spatiotemporally unrestricted. The traditional term for the kind, as employed by Aquinas and Kant, is “person” (cf. Hull 1986: 9).

Roger Scruton has recently taken this line, arguing that persons can only be adequately understood in terms of a web of concepts inapplicable to other animals, concepts whose applicability grounds in an essential moral dimension of the personal life form. The concepts pick out components of a life form that is permeated by relationships of responsibility, as expressed in reactive attitudes such as indignation, guilt and gratitude. Such emotions he takes to involve a demand for accountability, and as such to be exclusive to the personal life form, not variants of animal emotions (Scruton 2017: 52). As a result, he claims, they situate their bearers in some sense “outside the natural order” (Scruton 2017: 26). According to such an account, we should embrace a methodological dualism with respect to humans: as animals, they are subject to the same kinds of biological explanations as all other organisms, but as persons, they are subject to explanations that are radically different in kind. These are explanations in terms of reasons and meanings, that is, exercises in “Verstehen”, whose applicability Scruton takes to be independent of causal explanation (Scruton 2017: 30ff., 46).

Such an account demonstrates with admirable clarity that there is no necessary connection between a theory of “human nature” and metaphysical naturalism. It also reinforces the fact, emphasised throughout this entry, that discussions of “human nature” require both serious conceptual spadework and explicit justification of the use of any one such concept rather than another.

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• Wimsatt, William C., 2003, “Evolution, Entrenchment, and Innateness”, in Reductionism and the Development of Knowledge , Terrance Brown, and Leslie Smith (eds), Mahwah, NJ: Erlbaum, pp. 53–81.
• Winsor, Mary P., 2003, “Non-Essentialist Methods in Pre-Darwinian Taxonomy”, Biology & Philosophy , 18(3): 387–400. doi:10.1023/A:1024139523966
• –––, 2006, “The Creation of the Essentialism Story: An Exercise in Metahistory”, History and Philosophy of the Life Sciences , 28(2): 149–174.

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Aquinas, Thomas | Aristotle, General Topics: biology | Aristotle, General Topics: ethics | ethics: virtue | evolution | Kant, Immanuel | Locke, John: on real essence | naturalism: moral | natural kinds | psychology: evolutionary | species

Acknowledgments

I would like to thank Michelle Hooge, Maria Kronfeldner, Nick Laskowski and Hichem Naar for their comments on earlier drafts.

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4 Human Behavior: Nature or Nurture?

Learning Objectives

After reading this chapter, you should be able to:

• Describe Galton’s contributions towards the Nature and Nurture theory.
• Differentiate between the influence of genes and environment, as well as a combination of both.
• Define and Describe Epigenetics.
• Explain the difference between Social Learning Theory and Genetic Inheritance Theory.
• Explain the findings of the Bobo doll experiment.
• Understand the Grizzly Bear article.
• Understand the Beyond Heritability: Twin Studies article.
• Understand key concepts and definitions pertaining to nature vs nurture.

Introduction: What Do We Mean By Nature Vs Nurture?

In this chapter it is discussed that nature vs nurture is the debate of whether we are a product of nature (genetics) or nurture (environment). There is evidence supporting both sides of the debate. By the end of this, you should be able to determine that both nature and nurture play a key role in humans and animal behaviour.

Memory Match

The memory match game allows you to identify keywords pertaining to nature and nurture. The goal is to click a card and match the word on the card, with another card that has the same word. Now that you know how to play, let’s see how many you can match!

When we refer to nature, we are talking about our genetics that we inherit from our parents.  A fairly recent study (Kamran, 2016) conducted in Pakistan suggests that the parallels drawn regarding the temperament of siblings are due to their genetics. The results of this study states that the genetic makeup of relatives of the family (even deceased) also influence how the child acts. These behaviours of the child are identifiable by the family members even though the deceased family member no longer is present.

Browse through Galton’s timeline and discover his story!

Pair the Pioneer

The following pioneers play a key role in what we know about nature and nurture today! The goal of the game is to pair the correct pioneer with the correct fact pertaining to the pioneer. If you place your mouse above the pioneer, there is a fun fact that has a clue to help. Be careful, there is a trick pioneer!

• Nature:  refers to all of the genes and hereditary factors that influence who we are- from our physical appearance to our personality characteristics (definition retrieved from verywellmind.com on November 17, 2019).
• Epigenetics : the study of heritable changes in gene function that do not involve changes in DNA sequence (definition retrieved from MerriamWebster.com on November 17, 2019)

When we refer to nurture, we are talking about all the environmental factors that influence us. Environmental factors include but aren’t limited to parenting style, birth order, peers, family size, culture, language, education, etc. The main argument for nurture is that the environment is what makes us who we are. Those who are on the extreme side of nurture are empiricists. They believe humans are born as blank slates and acquire all information from their environment with their 5 senses.

Behaviorism, established by John Watson, is the theory that all behavior is a result of stimulation from the environment or a consequence of the individual’s previous conditioning. Behaviorism is a school of psychology that is on the side of nurture.

A study in 2019 performed an experiment on Bonobos (a species of chimpanzee) to observe social learning. The results of the experiment found supporting evidence that Bonobos are able to learn from observing others of their species just like humans.

Albert Bandura’s Social Learning Theory states that people learn by observing, imitating, and modeling behavior. In 1961, Bandura’s famous Bobo doll experiment’s findings support the argument for nurture in that our environment influences our behavior.

Key Terms: 

• Nurture: Environmental factors that influence our growth and behaviour.
• Empiricism: The belief that people are born as a blank slate learn everything from their environment.

Nature or Nurture? Or Both?

Given what we have discussed so far, is it genes or environment that influences behaviour? It is actually both genetic and social influences that contributes to an individual’s behaviour. Below is a video that explains how both components contribute to an individual.

Now that you understand how genes and environment work together, is it possible for one component to influence an individual more than the other? Below is an article that explains how grizzly bears’ conflict behaviour may attribute to genetic inheritance or social learning… talk about beary bad behaviour!

 Beary Bad Behaviour

Grizzly bear den

Welcome to the Grizzly Bear den. Inside there are paws, click any paw to learn key concepts within the article! Don’t worry, the bears won’t bite!

A study done in Alberta, Canada analyzed the genetic and environmental relationship of grizzly bears, pertaining to their offspring’s conflict behaviour. The study predicts that aggression is determined genetically from either biological parents. If the cub’s conflict behaviour is inherited from the father’s genes, then necessary relocation of wildlife protection is necessary to avoid human-conflict interaction. If the cub’s behaviour is inherited from the mother’s genes, then relocation of female bears is much more difficult to do as there are legal wildlife implications.

The study genotyped 213 grizzly bears, most of which were males. The study described conflict-beahviour or “problem bear” as those that exemplified invasive or aggressive behaviour on private property, public property, or had an incident with an individual. The results of the study indicated that the offspring of the female parent displayed a negative interaction more so than the offspring from the male parent.

According to Morehouse et al., (2016), “ results support the social learning hypothesis, but not the genetic inheritance hypothesis as it relates to the acquisition of conflict behaviour. If human-bear conflict was an inherited behaviour, we would have expected to see a significant relationship between paternal conflict behaviour and offspring behaviour.  Social learning has the potential to perpetuate grizzly bear conflicts highlighting the importance of preventing initial conflicts, but also removing problem individuals once conflicts start” (p.7). 

 Beyond Heritability: Twin Studies

In this study, it talks about the general observations of 50 study samples regarding over 800,000 pairs of twins and how their behavior may have been impacted by genes or by their environment. Due to the ethical limitations of human experimentation, there can only be a conclusion that there are mild causal effects. Heritable estimations are quite frankly useless in these studies because the results purely depend on the environmental conditions of the study participants, and it only becomes applicable when all participants are in the same environment.

If a separated teen is brought up in a rich environment, their gene makeup has a higher likelihood of being a factor in their upbringing. If his or her counterpart twin, in contrast, is brought up in a poor environment, the influence of their genes will be insignificant because of a less nurturing surrounding. Another example is the first sexual encounter on separated twins; do their shared genetics influence them to take action around the same time? The answer is no, because such events are a result of the environmental influences of delinquency.

Psychologist Eric Turkheimer states that there are essentially Three Laws of Behaviour Genetics:

“First Law: All human behavioural traits are heritable.

Second Law: The effect of being raised in the same family is smaller than the effect of the genes.

Third Law: A substantial portion of the variation in complex human behavioural traits is not accounted for by the effects of genes or families.”

He explains that genes only make up ~50% of our behaviours while the rest is influenced by our environment.

“The omnipresence of genetic influences does not [mean] that behaviour is less psychological or more biologically determined”, but it’s the facilitation of the environmental conditions that allows people to bring out their full behaviouristic tendencies to light; and even then, our genes are only half the story.

The following video is a study that looked at the effects of nature and nurture on twins. In short, there are many coincidences that may seem that their actions come from genetic relations.

• To answer the question of whether we are a product of Nature or Nurture, we are both. We are a product of our genetics, and our environment. Through our genetics, we have a certain baseline personality, but that changes over time due to the influence of our surroundings: the people we hang out with and the overall level of nourishment in our growing environment.
•  In summary, based on several studies and research it can be concluded that human behaviour is both nature and nurture. In addition, evidence also supports that animal behaviour specifically (grizzly bears) is also due to nature and nurture. Many aspects of the nature vs. nurture theory argues that various behaviours in humans are based both on genetics and the environment of an individual. However, it is possible that one variable from the theory may contribute more of an effect on the individual.

Chapter References

ABC News (2018, Mar 10) 20/20 Mar 9 Part 2: Adopted twins were separated and then part of a secret study. Retrieved November 17, 2019, from https://youtu.be/0-2FFsuitO4

Benjamin, J. (2017, March 31). Cancer: Nature Vs. Nurture. Retrieved November 17, 2019, from https://marybird.org/blog/olol/cancer-nature-vs-nurture

Biography.com Editors. (2019, August 28). Charles Darwin Biography. Retrieved November 17, 2019, from https://www.biography.com/scientist/charles-darwin.

Cherry, K. (2019, July 1). The Age Old Debate of Nature vs. Nurture. Retrieved November 19, 2019, from https://www.verywellmind.com/what-is-nature-versus-nurture-2795392.

David L, “Social Learning Theory (Bandura),” in Learning Theories, February 7, 2019, https://www.learning-theories.com/social-learning-theory-bandura.html .

Det medisinke fakultet. (2016, January 26). Epigenetics: Nature vs nurture. Retrieved November 17, 2019, from https://youtu.be/k50yMwEOWGU

Everywhere Psychology. (2012, August 28). Bandura’s Bobo Doll Experiment. Retrieved November 19, 2019, from https://youtu.be/dmBqwWlJg8U .

FuseSchool-Global Education. (2019, August 27). Nature vs Nurture | Genetics | Biology | FuseSchool Retrieved November 18, 2019 from https://www.youtube.com/watch?v=EmctxRcmloc

Gervais, M. (2017, August 31). Dr. Albert Bandura – The Theory of Agency. Retrieved November 19, 2019, from https://art19.com/shows/minutes-on-mastery/episodes/a1cef11d-e32c-4f03-ba4a-262a91268f4c.

Johnson W, Turkheimer E, Gottesman II, Bouchard TJ Jr. Beyond Heritability: Twin Studies in Behavioral Research.  Curr Dir Psychol Sci . 2010;18(4):217–220. doi:10.1111/j.1467-8721.2009.01639.x

Kamran, F., PhD. (2016). Are siblings different as ‘day and night’? parents’ perceptions of nature vs. nurture.  Journal of Behavioural Sciences, 26 (2), 95-115. Retrieved from https://ezproxy.kpu.ca:2443/login?url=https://search-proquest-com.ezproxy.kpu.ca:2443/docview/1864042019?accountid=35875

Merriam-Webster. (2019). Retrieved November 17, 2019 from https://www.merriam-webster.com/dictionary/epigenetics

McLeod, S. A. (2016, Feb 05). Bandura – social learning theory . Simply Psychology. https://www.simplypsychology.org/bandura.html

McLeod, S. A. (2018, Dec 20). Nature vs nurture in psychology. Simply Psychology. https://www.simplypsychology.org/naturevsnurture.html

Miko, I.  (2008)  Gregor Mendel and the principles of inheritance.  Nature Education   1( 1 ) :134

Morehouse, A. T., Graves, T. A., Mikle, N., & Boyce, M. S. (2016). Nature vs. nurture: Evidence for social learning of conflict behaviour in grizzly bears. PLoS One, 11 (11) doi:http://dx.doi.org.ezproxy.kpu.ca:2080/10.1371/journal.pone.0165425

Rose, H., & Rose, S. (2011). The legacies of francis galton. Lancet, the, 377 (9775), 1397-1397.doi:10.1016/S0140-6736(11)60560-6

Shorland, G., Genty, E., Guéry, J.-P., & Zuberbühler, K. (2019). Social learning of arbitrary food preferences in bonobos. Behavioural Processes, 167. https://doi-org.ezproxy.kpu.ca:2443/10.1016/j.beproc.2019.103912

TED-Ed. (2013, March 12). How Mendel’s pea plants helped us understand genetics. Retrieved November 17, 2019, from https://youtu.be/Mehz7tCxjSE.

Thesaurus.Plus . (n.d.). Retrieved November 17, 2019, from https://thesaurus.plus/thesaurus.

Turkheimer, E. (2000). Three laws of behavior genetics and what they mean.  Current Directions in Psychological Science ,  9 (5), 160–164. https://doi-org.ezproxy.kpu.ca:2443/10.1111/1467-8721.00084

Winch, J. (2012, Mar 08). Genius with a finger on the pulse of discovery: Birmingham-born sir francis galton was a victorian genius. but today he would be thought a racist because of the controversial interest for which he is best remembered – eugenics. jessica winch reports. Birmingham Post. Retrieved from https://ezproxy.kpu.ca:2443/login?url=https://search-proquest-com.ezproxy.kpu.ca:2443/docview/926809806?accountid=35875

Wikipedia. (2019, November 16). Francis Galton. Retrieved November 17, 2019, from https://en.wikipedia.org/wiki/Francis_Galton.

Evolutionary Psychology: Exploring Big Questions Copyright © by kristie. All Rights Reserved.

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Home — Essay Samples — Philosophy — Human Nature — Human Nature: The Eternal Debate of Good and Bad

Human Nature: The Eternal Debate of Good and Bad

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Inherent goodness: altruism and empathy, inherent badness: selfishness and aggression, the role of environment and culture, conclusion: the complexity of human nature.

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This article treats as separate various substantive spheres of human development (physical, perceptual, cognitive , linguistic, personality , and social), as it does various temporal phases of development (prenatal life, infancy, childhood, adolescence, adulthood, and old age). However, human beings are coherent wholes, and behavioral development is unified, so that development in any one arena of life at any one time is ineluctably interrelated with development in other arenas at the same and at other times in patterns of mutual influence. In the life course, genetic endowment and biology interact with cultural context and experience to shape the development of human behaviour. Each of these powerful sources of influence on development has distinctive characteristics, and it is their transaction over time as well as the degree of congruence between the two that influence outcome. Our elucidation of the processes that underpin human growth is central to understanding normal as well as abnormal development. Study of the development of human behaviour is unwieldy; life does not submit to elegant scientific analysis or to precise prediction. Therefore, developmental study takes as its goals the general description and explanation of origins, of constancy, and of change in perceiving, thinking , feeling , and behaving. Any such undertaking requires constant reconsideration in light of new data and new insights.

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For their last meeting of the fall 2023 semester, the students in MIT’s course 21W.756 (Nature Poetry) piled into a bus and headed to a local performance space for a reading: their own.

Sure, students in the course, taught by Professor Joshua Bennett, spend much of the semester reading and discussing poems. But they create and perform, too, often using tools from their other studies at MIT. One student in 21W.756 built a custom field microphone to incorporate recorded sounds into his work; another designed collages to complement her poems.

“The students are phenomenal,” says Bennett, a professor of literature and Distinguished Chair of the Humanities at MIT. “I try to think about how everything else they’re studying at MIT might meet up with the study of literature in a productive way. We’ve got great students who do super-interesting things.”

He adds: “They are willing to take the leap between other classes and our class very seriously. They see it as an opportunity — and they’ve explicitly told me this — to talk about being human. They’ve cherished that, and it’s been a transformative experience to have witnessed that.”

Bennett, an award-winning professor with a broad portfolio of work, knows about leaping between disciplines. He has published books of literary criticism, cultural history, and three collections of poems. Bennett has also gained renown as a spoken-word poetry performer — he has another major tour slated for this summer — and helped found the poetry collaborative Strivers Row. His readings have gained what must be millions of views on YouTube, including “ Tamara’s Opus ,” a dramatic work written for his deaf sister.

In short, Bennett also does his own super-interesting things, while encouraging students to join him in the pursuit of knowledge.

“Why do we create literature in the first place?” Bennett asks. “Why do we go to college? Why do we listen to people tell stories? Why do 300 or 3,000 people at a poetry reading listen to me or others talk? I imagine some of it is, there are things we love about being alive. And one of them is the feeling you can learn something new. You can be astonished. There is a space for you to become more complete through knowledge.”

Reading (and listening to) everything

Bennett grew up in Yonkers, New York, in a family that included preachers and musicians, and helped inculcate a love of learning in him.

“I’m thankful I had parents who just weren’t narrow-minded,” Bennett says. “They taught me to read everything, to listen to everything. At school I was reading Fitzgerald, and other works that were canonical, and wherever I saw beauty I really gravitated to it.” At the same time, he notes, “I was exposed to the genius of gospel music, jazz, and Motown,” while learning about Black scientists and much more.

He credits a 10th grade English teacher, Kaliq Simms, for helping him realize his potential as a student and writer.

“We read Hamlet, the Merchant of Venice, the Canterbury Tales, and she took us through literature in a way that made it land,” Bennett says. “She taught those works alongside Toni Morrison and James Baldwin. There was just something about the way she spoke to us. Ms. Simms said I was a ‘witty elocutionist.’ She just saw something in me other people didn’t see, or couldn’t. She had a serious role in changing my trajectory.”

Thus bolstered, Bennett earned his undergraduate degree as a double major in Africana studies and English from the University of Pennsylvania, where he became involved in the competitive poetry-slam scene. Bennett did so well as a performer that in 2009, before he had graduated, he was invited to perform “Tamara’s Opus” at the White House; it is an apology to his sister for not having learned sign language sooner. Graduating in 2010, Bennett was a commencement speaker at Penn.

If that weren’t enough, Bennett also earned a prestigious Marshall Scholarship, allowing him to receive an MA in theater and performance studies from the University of Warwick, in Coventry, England. Bennett then earned his PhD in English from Princeton University. His dissertation, about the place and meaning of animals in Black literature, ultimately became his 2020 book, “Being Property Once Myself.” It won the Modern Language Association’s William Sanders Scarborough Prize.

“It really emerged from having two grandparents who were sharecroppers who met in a strawberry field in North Carolina and emphasized the beauty of that field,” Bennett says. “I thought, how is that possible? To come out of that context with a story of love and beauty. When I got to Princeton, I expected the appearence of animals in African American literature to always be about degredation, but instead what I found were writers who took animals on their own terms, as beautiful, as powerful, as annoying, as recalcitrant, and sometimes as radicals or fugitives.”

Those writers include major figures such as Richard Wright, Zora Neale Hurston, Toni Morrison, Robert Hayden, and Jesmyn Ward, among others. “I chose all canonical authors, on purpose,” Bennett says. “But that was to say, these are some of the most written-about books by African Americans, and even so, people had not written about them in this way.”

After receiving his PhD in 2016, Bennett spent three years as a Junior Fellow in Harvard University’s Society of Fellows, then joined the faculty of Dartmouth College in 2019. Two years later, he was promoted to full professor. Bennett joined the MIT faculty full-time starting in 2023.

Among other recent honors, Bennett was awarded a Guggenheim Fellowship in 2021. He also won the 2023 Paterson Poetry Prize for his 2022 poetry collection, “The Study of Human Life.”

What kind of writing?

Bennett’s prolific output, both in scholarly works and as a poet and performer, no doubt owes much to his inner drive and enthusiasm. But his ability to produce work across genres also seems tied to his flexible thinking about writerly voice. Bennett is not constrained by the idea that his writing can only take one register; he varies his approach depending upon the project.

“To me it’s all [just] different kinds of writing,” Bennett says. “I was raised around musicians, around preachers, which I think is really central, because I understood what they were doing, even if some of them were improvising sermons, as a kind of writing. Poetry, fiction, and nonfiction are all kinds of writing, so [the question became], what kind of writing is best suited to my object of concern?”

For instance, Bennett says his 2016 poetry collection, “The Sobbing School,” a complex series of explorations about sustaining selfhood in the context of violence and tragedy, is about grief; that subject matter shaped the form.

“At that moment, I thought, these need to be elegies,” Bennett says.

However, Bennett’s 2023 nonfiction book “Spoken Word,” a history of the spoken-word poetry movement, is different. It is a deeply researched book that Bennett has written for a general audience, with a fast-paced text replicating the sense of movement and novelty surrounding the growth of the spoken-word genre, its best-known venues, like the Nuyorican Poets Café in Manhattan, and the creation of competitive poetry slams. In The New York Times , Tas Tobey called it a “vibrant cultural history.”

“I wanted to write ‘Spoken Word’ like a spoken-word poem, which I say explicitly, but I also wanted it to be a history of loving accomplishment,” Bennett says. “How people have not just competed, but worked together to create a sound.”

Another motif of “Spoken Word” is that in the process of creating spoken word poetry, people have found meaning in their own lives, discerned meaning in the works of others, and established human bonds and affinities and they might not have otherwise understood.

From the poetry slam venue to his own classroom, Bennett encourages this process. Making literature is an act of human value and meaning, and helps us reflect on it, too.

“We are here to sit with beauty and discomfort the whole time,” Bennett says of his class discussions. “Some of the work we read will be from people who were imprisoned, or enslaved, and we’re reading their poems together and learning what they have to say about human life.” Of his students, he adds: “We need as many hands on deck as possible, we need as many students who care and are devoted and as imaginative as possible in the room, and we need to give them all the resources we can to produce a livable world.”

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Elucidating the Hierarchical Nature of Behavior with Masked Autoencoders

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Natural behavior is hierarchical. Yet, there is a paucity of benchmarks addressing this aspect. Recognizing the scarcity of large-scale hierarchical behavioral benchmarks, we create a novel synthetic basketball playing benchmark (Shot7M2). Beyond synthetic data, we extend BABEL into a hierarchical action segmentation benchmark (hBABEL). Then, we develop a masked autoencoder framework (hBehaveMAE) to elucidate the hierarchical nature of motion capture data in an unsupervised fashion. We find that hBehaveMAE learns interpretable latents on Shot7M2 and hBABEL, where lower encoder levels show a superior ability to represent fine-grained movements, while higher encoder levels capture complex actions and activities. Additionally, we evaluate hBehaveMAE on MABe22, a representation learning benchmark with short and long-term behavioral states. hBehaveMAE achieves state-of-the-art performance without domain-specific feature extraction. Together, these components synergistically contribute towards unveiling the hierarchical organization of natural behavior. Models and benchmarks are available at: https://github.com/amathislab/BehaveMAE

Competing Interest Statement

The authors have declared no competing interest.

https://github.com/amathislab/BehaveMAE

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Effects of agriculture and nature reserves on avian behavior in northwestern Costa Rica

• Sollmann, Rahel
• Frishkoff, Luke
• Echeverri, Alejandra
• Karp, Daniel S.

Behavioral changes are often animals' first responses to environmental change and may act as a bellwether for population viability. Nonetheless, most studies of habitat conversion focus on changes in species occurrences or abundances. We analyzed >14,000 behavioral observations across 55 bird species in communities in northwestern Costa Rica to determine how land use affects reproductive, foraging, and other passive kinds of behaviors not associated with either foraging or reproduction. Specifically, we quantified differences in behaviors between farms, privately owned forests, and protected areas and implemented a novel modeling framework to account for variation in detection among behaviors. This framework entailed estimating abundances of birds performing different behaviors while allowing detection probabilities of individuals to vary by behavior. Birds were 1.2 times more likely to exhibit reproductive behaviors in forest than in agriculture and 1.5 times more likely to exhibit reproductive behaviors in protected areas than in private forests. Species were not always most abundant in the habitats where they were most likely to exhibit foraging or reproductive behaviors. Finally, species of higher conservation concern were less abundant in agriculture than in forest. Together, our results highlight the importance of behavioral analyses for elucidating the conservation value of different land uses.Efectos de la agricultura y las reservas naturales sobre el comportamiento de las aves en el noroeste de Costa RicaResumenLos cambios conductuales suelen ser la primera respuesta de los animales ante el cambio ambiental y pueden funcionar como un barómetro para la viabilidad poblacional. Sin embargo, la mayoría de los estudios sobre la conversión del hábitat se enfocan en cambios en la presencia o abundancia de las especies. Analizamos más de 14,000 observaciones conductuales en las comunidades de 55 especies de aves del noroeste de Costa Rica para determinar cómo el uso de suelo afectó el comportamiento reproductivo, de forrajeo y otras formas pasivas no asociadas con las dos anteriores. En específico, cuantificamos las diferencias en el comportamiento entre granjas, bosques de propiedad privada y áreas protegidas e implementamos un marco novedoso de modelado para justificar la variación en la detección entre los comportamientos. Este marco implicó estimar la abundancia de aves que realizaban diferentes comportamientos mientras permitía que variaran las probabilidades de detección de individuos según el comportamiento. Fue 1.2 veces más probable que las aves exhibieran comportamiento reproductivo en el bosque que en las zonas agrícolas y 1.5 veces más probable que exhibieran estos comportamientos en las áreas protegidas que en los bosques privados. Las especies no siempre fueron las más abundantes en los hábitats en donde era más probable que exhibieran comportamientos reproductivos o de forrajeo. Por último, las especies de mayor preocupación para la conservación fueron menos abundantes en las zonas agrícolas que en los bosques. En conjunto, nuestros resultados resaltan la importancia del análisis conductual para ilustrar el valor de conservación de los diferentes usos de suelo.【摘要】行为变化通常是动物对环境变化的第一反应, 可用于指示种群生存能力的变化。然而, 大多数关于栖息地转换的研究都侧重于物种的分布或丰度变化。本研究分析了哥斯达黎加西北部地区群落中55种鸟类超过14,000次的行为观察数据, 以确定土地利用类型对繁殖、觅食和除此之外其他被动行为的影响。具体来说, 我们量化分析了鸟类在农场、私有森林和保护地之间的行为差异, 并构建了一个新的模型框架来解释监测到的行为差异。该框架需要估计鸟类不同行为出现的丰度, 同时允许个体的监测概率因行为而异。结果显示, 鸟类在森林中表现出繁殖行为的几率是在农业区的1.2倍, 在保护地表现出繁殖行为的几率是在私有森林的1.5倍。而鸟类最有可能觅食或繁殖的栖息地, 物种丰度并不是最高的。最后, 农业区相比于森林, 出现的受保护程度较高的物种数量较少。总之, 我们的研究结果凸显了行为分析在阐明不同土地利用类型的保护价值方面的重要性。【翻译: 胡怡思; 审校: 聂永刚】

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• Published: 05 August 2024

Personalizing driver safety interfaces via driver cognitive factors inference

• Emily S. Sumner   ORCID: orcid.org/0000-0003-1912-9640 1 , 2   na1 ,
• Jonathan DeCastro 1 , 2   na1 ,
• Jean Costa 1   na1 ,
• Deepak E. Gopinath 1 , 2   na1 ,
• Everlyne Kimani 1   na1 ,
• Shabnam Hakimi 1 ,
• Allison Morgan 1 ,
• Andrew Best 1 ,
• Hieu Nguyen 1 ,
• Daniel J. Brooks 1 , 2 ,
• Bassam ul Haq 1 ,
• Andrew Patrikalakis 1 ,
• Hiroshi Yasuda 1 ,
• Kate Sieck 1 ,
• Avinash Balachandran 1 ,
• Tiffany L. Chen 1   na1 &
• Guy Rosman 1 , 2   na1  

Scientific Reports volume  14 , Article number:  18058 ( 2024 ) Cite this article

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Recent advances in AI and intelligent vehicle technology hold the promise of revolutionizing mobility and transportation through advanced driver assistance systems (ADAS). Certain cognitive factors, such as impulsivity and inhibitory control have been shown to relate to risky driving behavior and on-road risk-taking. However, existing systems fail to leverage such factors in assistive driving technologies adequately. Varying the levels of these cognitive factors could influence the effectiveness and acceptance of ADAS interfaces. We demonstrate an approach for personalizing driver interaction via driver safety interfaces that are are triggered based on the inference of the driver’s latent cognitive states from their driving behavior. To accomplish this, we adopt a data-driven approach and train a recurrent neural network to infer impulsivity and inhibitory control from recent driving behavior. The network is trained on a population of human drivers to infer impulsivity and inhibitory control from recent driving behavior. Using data collected from a high-fidelity vehicle motion simulator experiment, we demonstrate the ability to deduce these factors from driver behavior. We then use these inferred factors to determine instantly whether or not to engage a driver safety interface. This approach was evaluated using leave-one-out cross validation using actual human data. Our evaluations reveal that our personalized driver safety interface that captures the cognitive profile of the driver is more effective in influencing driver behavior in yellow light zones by reducing their inclination to run through them.

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Improvements in advanced driver safety assistance systems have the potential to save lives 1 , 2 . However, these safety systems could benefit from targeting the cause of individual drivers’ dangerous driving behavior, which is known to be affected by many different factors, including cognitive, social, and situational 3 , 4 , 5 . Among the cognitive factors that influence risky driving behavior are cognitive impulsivity , which is the tendency to act without thinking 6 , and inhibitory control , which is the ability to suppress goal-irrelevant stimuli and behavioral responses 7 . Risky driving has been associated with higher self-reported impulsivity 4 , 8 , 9 , 10 , 11 , and with poorer inhibitory control in relevant laboratory tasks 4 , 10 , 11 , 12 , 13 . A recent review has shown the relationship between impulsivity and speeding and other driving violations 14 . More recent work has emphasized that the relationship between impulsive processes and driving errors and violations is influenced by cognitive abilities and self-regulation 15 , 16 . Further, such effects are associated with both sensation seeking (a concept related to impulsivity) and age, with recent work demonstrating that higher sensation-seeking and younger age were predictive of the highest speed during driving on a virtual reality track 17 . These cognitive factors also influence individuals’ reactions to different types of interfaces 18 , 19 .

Paaver et al. 20 showed that even a brief classroom-style lesson on impulsivity and driving can prevent speeding. Although the significance of impulsivity and inhibitory control as risk factors for vehicle accidents has not yet been leveraged in ADAS interfaces, these concepts have been used to develop effective driver educational materials. While there are numerous driver safety interfaces available, there is a gap in the research regarding the influence of impulsivity and inhibitory control on drivers’ responses to these interfaces. More specifically, studies have not adequately explored how to tailor the deployment of these safety interfaces to individual drivers, taking into account their unique levels of impulsivity and inhibitory control. Such personalization is crucial, as it can determine the effectiveness of the interface in enhancing driver safety.

Thus, the efficacy of driver safety systems may vary due to individual differences in cognition. The design of human-machine interfaces (HMIs), with a focus on addressing specific cognitive characteristics, has the potential to enhance both their safety effectiveness and user acceptance 21 . Crucially, the ability to estimate cognitive characteristics from observed driver behavior lays the groundwork for more personalized and effective safety interventions.

Our goal is to build a driver safety system that leverages learned representations of individual drivers’ cognitive factors to personalize HMIs that result in safer driving outcomes. Such a system would allow us to fully separate the underlying reasons for personalization (i.e., the learned cognitive factors) from what specific HMI attributes are personalized as a result of those reasons. This approach, in turn, allows for the deployment of highly versatile safety systems - for instance, if a new HMI is developed, these can be integrated without additional re-training of the underlying representation. The neural representations of cognitive factors enable refinement of the estimated factors, as well as deployment of personalized safety intervention, at large scale.

In this paper, we present experimental evidence for how factors such as impulsivity and inhibitory control can influence people’s responses to driver safety interfaces and how the inference of such cognitive measures enables an approach for personalizing safety interfaces. We do so by constructing a neural network model that embeds driver behavior into a latent space that captures these factors; finally, we demonstrate the embedded representation’s utility for triggering the deployment of assistive driving interfaces targeted to inhibitory control and impulsivity. To our knowledge, we are the first to demonstrate driver assistance personalization in a high-fidelity simulator.

In this paper we contribute: (1) Experimental evidence of how impulsivity and inhibitory control relate to performance under different choices of driver safety systems on a new dataset collected in a large-scale, high-fidelity, driving simulator; (2) A neural network model capable of encoding individual cognitive factor differences based on recent driving behavior; and (3) A decision-making system capable of personalizing the activation of driver safety interface based on the inferred cognitive factors.

Related works

Our work is at the intersection of two active research areas: the role of cognitive factors in understanding driving behavior, and learning approaches that capture specific latent factors for HMIs.

Cognitive factors and driving behaviors Common approaches for assessing driving behavior commonly involve self-report surveys 22 , ticketed speeding violations 23 , or crash records 24 . While these measurements can be good indicators of risky driving behavior, self-report metrics such as these are not always reliable 25 , contain private information, and do not lend themselves to seamless integration into preventative use with drivers. Other studies have shown driving characteristics can be estimated by measuring reactions to predetermined unsafe events in a simulated driving task 12 .

Our work provides a comprehensive general approach (Fig. 1 ) to inferring latent cognitive factors from driving behavior logs via a neural network encoder, and uses a high-fidelity driving motion simulator where behavior is closer to real-world vehicles than in lower-fidelity simulators (e.g., bench set up with a steering wheel) (Fig. 3 c).

A conceptual overview of our framework. Latent factors embed cognitive measures from the driving behavior, and used to inform HMI choice(dashed lines). Solid line marked the observable driving behavior and personalized HMI.

In addition to measuring driving behavior, researchers often measure impulsivity and other behavioral and cognitive factors via tests and questionnaires 26 , 27 , 28 , 29 . However, for these cognitive factors to effectively enhance vehicle safety systems, they should be estimated in a scalable way and applied to the development of personalized assistive interfaces within vehicles. In our work, we adopt a data-driven approach to train a neural network model that estimates cognitive factors from driving behavior (as opposed to relying on tests and questionnaires) thereby lending itself to deployment at scale. This could lead to more accurate information about drivers and further lead to effective intervention design and deployment criteria.

Learning Latent Factors for Human-Machine Interfaces Since an intelligent vehicle is a robotic system, our approach also relates to efforts in personalizing interactions between humans and robots or other machines. Prior work in machine learning for HMIs and human-robot teaming has focused on various human-robot interaction modalities such as driver monitoring, optimal shared control laws, and design of assistive robot behaviors (see e.g. 30 , 31 , 32 , 33 ). However, these approaches for human-robot interactions typically do not explicitly consider individual differences in cognitive factors and therefore fall under the category of a “one-size-fits-all” design.

The same is true for modern-day driver assistance systems such as lane-departure warnings or forward-collision warnings. Typical interventions issued by such systems depend on an individual’s state and action history and manifest as corrections of unsafe or suboptimal human actions generated from a policy learned from a desired set of behaviors required of the system 34 . Such approaches have been found to over-fit to the average-case behavior of individuals in a population, leading to incorrect inference of the human’s state and poor generalizability 35 , 36 . Given both the safety risks and the high degree of individual variation in factors like impulsivity and inhibitory control, over-fitting can have potentially dire consequences for drivers 37 . Recent work has shown that learning latent representations summarizing human behavior can improve teaming and interaction with the human. For instance, work on dialog systems 38 , recommender systems 39 , 40 , and intent recognition for products and motion 41 , 42 have demonstrated that latent representations are capable of better predicting the user’s need for a given intervention and their reaction to that intervention. We posit that using this representation as a basis for deciding whether to interact and which modes of interaction to use should improve safety over “one-size-fits-all” decision schemes.

In this paper, we explore how to effectively personalize HMIs based on people’s impulsivity and inhibitory control. We posit that latent factors such as impulsivity and inhibitory control can be inferred in an automated manner from driving behavior and can inform choices of interactions with the drivers to benefit them at a large scale.

Computational model

We now proceed to describe our computational approach for encoding latent cognitive factors. The resulting neural network distills a human driver’s recent driving history down to a low-dimensional parameter space whose structure can be easily shaped via multiple cognitive measures in a semi-supervised manner. The model we use includes a context encoder whose input is a time-receding, fixed-window trajectory of driving behavior in a scenario and whose output is a low-dimensional latent vector. This latent representation is then coupled with a separate decision-making module that takes this latent vector as input and outputs a decision at each decision time-step; for instance, whether or not to present a particular HMI to the driver at the current time-step. The architecture is shown in Fig.  2 , with further details in the “ supplemental information ”. As a result of experimentation, we found that a two-dimensional latent vector provided sufficient capacity to capture relevant cognitive factors, yet allow direct interpretation of the learned trends in the representation without possible distortions introduced by dimensionality reduction schemes (e.g. t-distributed Stochastic Neighbor Embedding 43 ).

The context encoder is represented as a long short-term memory (LSTM) recurrent neural network 44 , \(q_{\psi }(z \mid \tau )\) , and defines the probability of latent vector z given a past trajectory \(\tau\) of the driver.

The hidden layer h is fed into two linear layers that output the mean and log-variance of the latent encoding 45 .

As driving actions do not directly relate to psychological traits, we leverage contrastive learning 46 , 47 to encourage the latent representation to conform to measured cognitive factors (we introduce the specific factors we use in the Results section). As decisions should be based on more than one cognitive factor, we consider our cognitive factor target to be a vector.

The context encoding model transforms a driver’s past driving history \(\tau\) to a latent vector z , and uses a decoder network \(p_{\theta }(a|z)\) to predict the driver’s action a at the current time-step. We set up the loss terms to encourage z to capture both the individual’s cognitive factors and reconstruction of driver actions, with the factors allowing for the downstream decision-making module to have awareness of any time-independent factors inherent to the individual driver, as well as driver actions allowing for awareness of the behaviors in a given situation. Any scene context information present in \(\tau\) will indirectly manifests in z through \(q_{\psi }(z \mid \tau )\) . Thus, we expect a weak dependence of predicted driver action on scene context. The overall loss used to train the encoder consists of three components:

\(L_1(a, z; \theta ) = -\mathbb {E}_z \log p_{\theta }(a \vert z)\) is the expected negative log likelihood of action a under the model (reconstruction loss) induced by the conditional distribution p over z , where z characterizes driving behavior up to time t and \(\theta\) represents the parameters of the action decoder network.

\(L_2(z,y;\psi)\) , a contrastive loss supervised using a vector of cognitive factor targets y 48 . For continuous-valued cognitive measures, this loss is

where \(\mathcal {Z}\) represents a training samples batch, where each independently-sampled \(z, z' \in \mathcal {Z}\) is a \(\vert Z \vert\) -dimensional latent vector induced by the LSTM context encoder with parameters \(\psi\) , \(y_{z}\) is a vector of batch-normalized cognitive measures associated with z , \(\ell (z, z')\) is a measure associated with two vectors z and \(z'\) (which we choose as their Euclidean distance, i.e.  \(\Vert z - z'\Vert\) ), and \(\epsilon\) controls the magnitude of dissimilarity of y -values in z -space, where a larger \(\epsilon\) enforces higher separation of \(\Vert z - z'\Vert\) for fixed \(\Vert y_{z} - y_{z'}\Vert\) .

\(L_3(z) = D_{KL}(q_{\psi }(z \mid \tau )\vert \mathcal {N}(0,I))\) , a Kullback-Leibler (KL)-regularization loss for the distribution of z , e.g. as in 49 , 50 . \(\mathcal {N}(0, I)\) is the unit-normal distribution of appropriate dimension.

These terms are combined into an overall training loss:

where \(\alpha _1\) , \(\alpha _2\) , and \(\alpha _3\) are the respective loss coefficients.

Overall system architecture, including context encoder, decoder for future state and action prediction, outputs of cognitive measures, and latent factors used for HMI selection and decision-making.

HMI Decision-Making : We evaluate the utility of the inferred latent factors model by marrying it with a decision rule for selecting the activation of the HMI. The decisions are defined via a simple classifier whose inputs are the inferred latent factors. The classifier is trained to optimize a criterion for HMI selection within the training data. We take the criterion for classification to be the difference in average speed between two conditions, with and without HMI, when the yellow light is active, (averaged across trajectories for a single subject). This criterion reflects the speed reduction induced in the subject when an HMI is presented to the driver. Therefore, for each subject, we have a single regression target and the decision maker is trained to map the latent factors inferred from that subject’s trajectory snippets around yellow light transitions to the corresponding regression target; essentially learning a many-to-one function. We use Support Vector Regression 51 with a polynomial kernel as our decision model.

Behavioral experiment

Our motion-simulator driving experiment was designed to address the following hypotheses:

People with different levels of cognitive factors should exhibit different driving behaviors.

People with different levels of cognitive factors should respond differently to HMIs.

Our model should infer individual differences in cognitive factors from driving behavior data.

When using our model of inferred cognitive factor differences to choose HMIs, and those choices should result in lower speeds when passing through traffic lights.

The goal of our experiments is to validate H1–H4 by performing the following: (1) constructing candidate HMIs using a simple hand-crafted decision rule to time the deployment of the HMI for alerting the driver when they were approaching a traffic light to influence their driving behavior (specifics can be found in Fig.  3 e, (2) data collection of unassisted, baseline driving behaviors from a variety of types of individual drivers in a simulated road setting involving traffic lights, (3) data collection of driving behaviors with the HMI assistance schemes, (4) utilizing the collected data for training a model that encodes cognitive traits, as measured by cognitive assessments, from driving behavior.

In post-hoc, retrospective, analysis of the data, we conducted: (5) post-hoc evaluation of the HMI effect on driver behavior on approach to traffic lights, (6) post-hoc evaluation of our encoding of cognitive traits with respect to cognitive assessments, and (7) post-hoc evaluation of individuals’ behavioral response with the provided HMIs and using the models. Due to the logistical constraints associated with including more participants in our study, we designed our experiments to use a single pool of subjects to address each tasks (1)–(7). Hence, we conduct a randomized study involving each candidate HMIs without using the cognitive inference model. Data collected from the study was used to train a neural network-based cognitive inference model. The model was validated using a leave-one-out cross-validation scheme with respect to a chosen behavior statistic (mean speed during yellow light phase), in retrospect, by averaging over trials in which the experimental condition matched the model’s decision.

Participants

Thirty-nine Northern California-based drivers aged 18 and older ( Mean age = 49, Female = 16, Non-binary = 1 ) were recruited to participate in our study via Fieldwork, a global market research firm. Participants were only invited to participate if they held an active driver’s license, were not pregnant, and were vaccinated for COVID-19. Further details can be found in the recruitment section in the “ supplemental information ”.

Half of the participants were between the ages of 18–22, the other half were over the age of 65. We chose to recruit these two age groups because previous research has shown significant differences in their levels of impulsivity, inhibitory control, and risk propensity. 52 Additionally, these two populations are at heightened risk of vehicle accidents 11 . We opted to start with these groups to determine if there is a detectable signal. While age-related differences are not discussed in this paper, additional analyses can be found in the “ supplemental information ”. We did not find any significant differences between these two populations in our analysis.

This research was reviewed, approved, and done according to the human-subject guidelines set by the Western Institutional Review Board-Copernicus Group (WCG) IRB protocol number 20221727. Participants filled out a consent form prior to participation and were compensated $150 for their two-hour participation.

Exclusion criteria

Participants were excluded from the analysis if they did not complete the study. Of the 39 participants, 7 participants did not complete the driving trials due to motion sickness. Of the 32 remaining participants, the data of 5 participants was excluded from the analysis due to technical difficulties with the motion simulator during testing. The final sample size was therefore 27 individuals.

Driving task

As illustrated in Fig.  3 d, participants drove on a looped road with traffic lights that randomly changed from green to yellow at varying times of arrival of the vehicle at the traffic light, inducing a zone of dilemma 53 (See Fig.  3 d). Each loop consisted of eight traffic lights, four of which would turn yellow. The driving time during the laps summed over all participants was 540 min, which has been shown to be sufficient for driver behavior estimation in similar driving conditions 54 . We collected four driving trials (laps) where participants interacted with different prototype driver safety interfaces and two baseline driving laps without the interfaces.

Motion simulator

Participants completed the driving portion of the task using our vehicle motion simulator (See Fig.  3 c 55 , 56 , 57 ). The motion simulator has a cabin with two car seats, a steering wheel, and pedals that resemble the front half of a vehicle. The cabin is supported by a 6 DOF Motion Platform 58 and actuated based on the simulated vehicle movement in a virtual traffic environment. The cabin is surrounded by a projection screen that shows the virtual traffic environment. The CARLA simulator controls the virtual traffic and renders high-fidelity visuals by Unreal Engine 59 . A control booth behind the cabin allows the experimenter to control the scenarios and monitor participant safety. Communication between the experimenter and participant is enabled through a headset that is connected to a microphone and speakers in the cabin.

Driver safety interfaces

Two types of warning interfaces were used: a) transverse markings, projected on the road the car was driving; and b) a 2D yellow circle, projected as if it appeared in a heads-up display. Figure  3 e shows the virtual scenario and both interface types. The first two laps had no interfaces. The purpose of the first baseline lap was for the participant to get acclimated to the simulator and get a feel for how it drives and not included in analysis. For each interface, we also manipulated a trigger condition that determined whether or not it was displayed. Each interface was displayed either when the vehicle approached the traffic light (185 meters away) or when the upcoming traffic light changed from green to yellow.

Impulsivity: To assess participants’ impulsivity 60 , we used the BIS/BAS scale and the UPPS-P scale. The BIS/BAS was used to measure both the behavioral inhibition system (BIS) and the behavioral activation system (BAS), while the UPPS-P was used to account for different facets of impulsivity 61 .

Inhibitory Control: We used the Go-No Go task 62 and the Stop Signal task 63 , 64 to measure response inhibition. Stop Signal task measures were as described by Verbruggen et al. 64 .

Self-reported Driving Behavior: To assess participants’ road errors and violations, we used the Manchester Driver Behavior Questionnaire (DBQ) 22 . It includes four sub-scales that measure driver errors (such as failing to check your mirrors), lapses (such as turning the wrong blinker on), aggressive violations (such as racing other vehicles on the street), and ordinary violations (such as ignoring the speed limit on the highway).

Driving Behavior in the Motion Simulator: We also captured driving behavior as participants drove in the motion simulator. We recorded their driving speed, acceleration, and response to yellow traffic lights.

( a ) Participant overview. ( b ) Set of surveys used to measure latent cognitive factors. ( c ) An illustration of the driving motion simulator used for data collection. ( d ) Driving task course overview. For each lap, four of the lights would transition from green to yellow to red; these were randomly selected for each trial. ( e ). Set of HMIs presented in the driving task. Participants would complete two baseline laps to start. The first baseline lap was considered practice to get the driver acclimated to the simulator and was not included in analysis. After the second baseline lap, the four HMI trials were randomized in the order they were presented to the driver.

The effect of different HMI types on the mean speed during the lap. “D” refers to a distance-based trigger of the HMI, where the HMI is presented when the vehicle enters within 185 meters of the traffic light, and “L” refers to a light-based trigger, where the HMI is presented at the moment the traffic light turns from green to yellow. Each box plot displays the median, interquartile range (IQR), and outliers for the mean speed during these conditions.

We analyzed the relationship between various aspects of impulsivity, inhibitory control, driving behavior, and responses to HMIs designed to encourage drivers to slow down. We then analyzed the performance of our model in inferring participants’ cognitive factors and predicting whether they should interact with a HMI to support driving goals.

Relationship between cognitive factors and driving behavior (H1)

To understand the relationship between the different cognitive factors and driving behavior when reacting to the yellow lights, we conducted a Bayesian correlation analysis using the JASP software 65 . For the analysis, we used the data from all of the driving laps – including the ones with HMIs presented. A table with all of the Bayesian correlations can be found in the “ supplemental information ” document. As shown in these tables, a number of significant correlations emerged.

The self-reported ordinary violations (errors such as speeding or staying close to another vehicle you are behind) measured in the DBQ 22 were (mean = 12.778, sd = 1.819) positively correlated with the mean speed at the yellow light (r = 0.4, BF10 = 9693) and the maximum speed when the yellow was active light (r = 0.54 BF10 = \(1.141\times 10^9\) ), indicating that drivers who reported higher levels of ordinary violations from the DBQ (mean = 13.556, sd = 4.348) were more likely to speed through yellow lights in this task.

We found several correlations between the BIS/BAS measures and driving behavior. In particular, BAS Fun Seeking mean = 11.704, sd = 2.165 was positively correlated with the mean speed at the active yellow light (r = 0.473, BF10 = \(1.700\times 10^6\) ) and the maximum speed at the yellow light (r = 0.31, BF10 = 99.19). These data suggest that individuals who have a higher desire for new and exciting experiences may be more likely to take risks while driving, such as speeding through yellow lights. BAS Reward Responsiveness (mean = 16.741, sd = 1.740) was also positively correlated with the maximum speed at an active yellow light (r = 0.29, BF10 = 39.63).

Similar to the BIS/BAS measures, various correlations emerged using the UPPS-P subscales. For instance, UPPS-P Positive Urgency (mean = 6.630, was positively correlated with the maximum speed at an active yellow light (r = 0.28, BF10 = 26.93), and UPPS-P Sensation Seeking (mean = 11.000, sd = 3.150) was positively correlated with the mean speed at the active yellow light (r = 0.29, BF10 = 42.89) and the maximum speed at the active yellow light (r = 0.47, BF10 = \(1.540\times 10^6\) ). These results are consistent with the results found for BAS Fun Seeking (mean = 11.704, sd = 2.165) and BAS Reward Responsiveness (mean = 16.741. sd = 1.740), which provides further evidence that people who desire fun, new and thrilling experiences are more likely to speed and take risks when reacting to traffic lights.

Multiple correlations also emerged using the measures from the Stop Signal task. For instance, the reaction time on go trials with a response (goRT_all, mean = 618.148, sd = 170.594) was negatively correlated with the mean speed at the yellow light (r = \(-\)  0.38, BF10 = 2933). This suggests that drivers with longer reaction times may be more likely to slow down at yellow lights rather than speeding through them.

Finally, we also found numerous correlations using the Go/No-Go measures. Among the correlations, the average response time (gonogo_average_rt, mean = 382.981, sd = 49.262) was negatively correlated with the mean speed at the yellow light (r = \(-\)  0.46, BF10 = 352747) and the maximum speed at the yellow light (r = \(-\)  0.40, BF10 = 9205), which is consistent with the reaction time results from the Stop Signal task (e.g. goRT_all).

Interaction plots showing how the presence of the HMI interacted with different measures. The lines represent different levels of the measures: +1 SD (High), Mean, and -1 SD (Low). From left to right, the measures are: ( a ) BAS Fun Seeking: Motivation to find novel rewards spontaneously; ( b ) SSRT: Stop Signal Reaction Time: Ability to inhibit a response; ( c ) UPPS-P Positive Urgency: Tendency to act impulsively due to positive affect; d) DBQ Ordinary Violations: Self-reported ordinary driving violations.

Impact of cognitive factors on people’s driving responses to the interfaces (H2)

We fitted separate linear mixed models to predict each driving behavior measure based on interface condition (Table  1 ). All conditions demonstrated a statistically significant and negative effect on the mean speed during the lap, as depicted in Fig.  4 .

To further understand how different factors affect drivers’ responses to HMI, we conducted a linear mixed models (LMM) analysis, using multiple LMMs to examine the effects of various factors, including the presence or absence of HMI ( HMI_presence ) and their potential interactions. Participant ID was used as a random effect to account for individual differences. The lmer function in the lme4 R package 66 was employed for predicting mean speed when yellow lights were active based on these variables as

where \((1 | \text {Participant})\) denotes the random intercept. The models were fitted using the Restricted Maximum Likelihood (REML) estimation method, and the t-tests utilized Satterthwaite’s approximation method.

For detailed statistical outcomes, please refer to Table 1 . For a visual representation of some interaction effects, please see Fig.  5 , which complements the textual analysis. Here, we highlight some key findings that were noted to have a strong effect:

BIS/BAS : The BAS Fun Seeking subscale showed a significant main effect of HMI presence ( \(\beta = -11.14\) , \(SE = 4.64\) , \(t = -2.4\) , \(p = 0.018\) ) and a significant interaction with BAS Fun Seeking ( \(\beta = 0.9\) , \(SE = 0.39\) , \(t = 2.31\) , \(p = 0.023\) ), suggesting that individuals with higher BAS Fun Seeking scores drove faster in the presence of HMI compared to those with lower scores. The fixed effects accounted for 22.5% of the variance ( \(R^2_m = 0.225\) ), while the combined fixed and random effects accounted for 75% ( \(R^2_c = 0.75\) ).

UPPS-P : The Positive Urgency subscale revealed a significant main effect of HMI presence ( \(\beta = -8.71\) , \(SE = 2.66\) , \(t = -3.28\) , \(p = 0.0014\) ) and a significant interaction with Positive Urgency ( \(\beta = 1.23\) , \(SE = 0.38\) , \(t = 3.22\) , \(p = 0.0017\) ), indicating that individuals with higher Positive Urgency scores drove faster in the presence of HMI. The fixed effects explained 2.2% of the variance ( \(R^2_m = 0.022\) ), while the combined fixed and random effects explained 76.4% ( \(R^2_c = 0.764\) ).

Go/No-Go Measures : The Go/No-Go Average Response Time measure showed no significant main effect of HMI presence ( \(\beta = -0.85\) , \(SE = 6.88\) , \(t = -0.124\) , \(p = 0.9019\) ), but a significant effect of response time ( \(\beta = -0.072\) , \(SE = 0.028\) , \(t = -2.57\) , \(p = 0.0139\) ), indicating that longer response times were associated with slower driving speeds. The interaction between HMI presence and response time was not significant ( \(\beta = 0.00017\) , \(SE = 0.018\) , \(t = 0.010\) , \(p = 0.9922\) ). The fixed effects explained 20.4% of the variance ( \(R^2_m = 0.204\) ), while the combined fixed and random effects explained 74.0% ( \(R^2_c = 0.740\) ).

Stop Signal Measures : The SSRT measure showed no significant main effects of HMI presence ( \(\beta = 3.69\) , \(SE = 2.29\) , \(t = 1.61\) , \(p = 0.1094\) ) or SSRT ( \(\beta = 0.0145\) , \(SE = 0.0131\) , \(t = 1.11\) , \(p = 0.2724\) ). However, a significant interaction between HMI presence and SSRT was observed ( \(\beta = -0.0147\) , \(SE = 0.0073\) , \(t = -2.01\) , \(p = 0.0471\) ), suggesting that individuals with higher SSRTs drove slower in the presence of HMI compared to those with lower SSRTs. The fixed effects explained 1.0% of the variance ( \(R^2_m = 0.010\) ), while the combined fixed and random effects explained 75.1% ( \(R^2_c = 0.751\) ).

Manchester DBQ : The DBQ Ordinary Violations subscale showed a significant main effect of HMI presence ( \(\beta = -6.99\) , \(SE = 2.76\) , \(t = -2.53\) , \(p = 0.0128\) ) and a significant interaction with Ordinary Violations from the DBQ ( \(\beta = 0.473\) , \(SE = 0.194\) , \(t = 2.44\) , \(p = 0.0164\) ), suggesting that individuals with higher Ordinary Violations on the DBQ scores drove faster in the presence of HMI. The fixed effects explained 16.4% of the variance ( \(R^2_m = 0.164\) ), while the combined fixed and random effects explained 75.2% ( \(R^2_c = 0.752\) ).

Computational model results: inferring inhibitory control and HMI choice from driving behavior (H3, H4)

Given the various measures collected in the study, we used stepwise regression to select the most important features for training our neural-network based cognitive factor inference model. We combined forward selection, starting with an empty model and adding the predictor that produced the largest increase in model fit, with backward elimination, removing the predictor that produced the smallest decrease in model fit until no further improvement was observed. By following this process, the stepwise regression yielded a set of four cognitive factors to be used in the model: UPPS-P - Positive Urgency, BAS Fun Seeking, goRT_all, and DBQ - Ordinary violations.

We adopt the learning approach described to infer cognitive factors based on the subjects’ driving during the experiment. As mentioned earlier, we use the same data to perform training and evaluate model inference. In order to fairly conduct the evaluation, we perform leave-one-out cross-validation over the 27 subjects, averaging model performance over 10 random seeds, and capture properties of the embedding and the resulting training decision criteria performance. We include a complete description of the training and evaluation steps and further findings in the “ supplemental information ”. The distribution of the inferred latent factors is shown in Fig.  6 a. Qualitatively, we observe that fairly strong clustering has emerged for each of the cognitive factors which indicates the effectiveness of the contrastive learning approach is effective. To quantify this further, we show in Table  2 the fit between the distribution of the selected cognitive and the inferred latent factors. Since there is no direct or linear mapping assumed in contrastive learning, we probed the uniformity of the inferred embedding. We used the KL distance between the cognitive measures and the inferred factors’ distribution. The results demonstrate the model’s ability to infer several variables interest centered around impulsivity and inhibitory control.

We next proceed to probe the efficacy of the resulting latent space to inform HMI adaptation to the subjects. We use leave-one-out to evaluate the decision classifier based on the inferred latent factors. From the test subject’s data, we extract trajectory snippets around the yellow light transitions. The segment of the trajectory before the transition is fed into the context encoder to generate an inferred latent factor. The decision classifier subsequently consumes this latent factor to produce the HMI decision. In order to evaluate the interface selection decisions by the decision classifier we compare them to fixed interface choice chosen optimally for all participants (“one-size-fits-all” approach). We then measure the participants’ behavior in terms of our chosen behavior statistic (mean average speed when yellow light was active) for the selected HMI choice (the classifier’s decision) for the withheld subject averaged over the trials in which the experimental condition matched the decision classifiers output (thereby treating the experiment as a within-subject randomized trial study).

We measure performance of the decision scheme with three metrics: mean yellow light speed, reporting mean ( \(\mu\) ) and standard deviation ( \(\sigma\) ) aggregated over individuals, along with a Cohen’s \(\kappa\) and Balanced Accuracy scores that measure, respectively, accuracy of interface selection scheme under an unbalanced dataset. When leveraging the latent factors to decide on an HMI choice, we achieve a balanced accuracy of 56% and a Cohen Kappa of 0.145 in selecting the optimal HMI for the specific driver, as shown in Table  3 , resulting in a reduction of 0.59 m/s in the mean speed throughout the yellow-phase of the traffic light. Additionally, in Fig.  6 b (left), we code each of the latents generated from the trajectory snippets according to the decision module’s predictions. In conjunction with Fig.  6 b (right), the trajectory snippets for which deployment of the HMI was the decision, we see that the average speed after the yellow light transitions is lower, showing the effectiveness of the HMI decision scheme. The color distribution in the different plots demonstrate how the embedding space captures both the driver traits as captured in the questionnaires (a), and the chosen interface decision and resulting driver speed at the yellow light interval (b).

Example embedding and decision module result based on training data from a 27-subject fold; ( a ) Embedding of participants’ past history trajectories with contrastive loss based on four factors: goRT all, UPPS-P Positive Urgency, DBQ Ordinary Violations, and BAS Fun. Colors mark low (red) to high (blue) measures; ( b ) Trained decision boundary (left) and average speed during the yellow light phase conditioned on the decision scheme (right), plotted on the latent embedding space \(z_0\) , \(z_1\) . Each point represents a unique time window over which the inference was run.

Limitations

Despite efforts to include a large sample for our study, our sample size was relatively small. Some of this is due to participant motion sickness which at times was quite severe participation had to be ended early. We highlight that this is due to various logistical limitations such as the high costs involved in running a high-fidelity motion simulator study, COVID-related restrictions in recruiting human subjects and the need to implement in-lab social distancing measures, and the technological setup involved with a high-fidelity simulator. We also reiterate that some exclusion of participants was necessary, given our prioritization of a sound dataset over a larger one. While our sample size is in line with what others use in driving simulator studies 67 , 68 , or machine-learning driving behavior research 69 , 70 , it is still a relatively small population. We limited our experiment to older and younger participants thinking there would be a larger effect between these two groups. Although this effect did not appear related to age, we found an effect independent of age. Future work should expand the sample to a larger and more representative sample to look at the generalization of these findings. Since our analysis shows promise, a follow-up examining the algorithm’s decisions in real-time would be warranted.

As traffic accidents and violations frequently occur due to poor impulsivity and inhibitory control, it is important to create driver safety systems that can overcome these cognitive limitations on a personalized level. In this work, we present an approach to infer the individual’s latent factor, the use it to decide when it is or is not appropriate to show a driver safety interface depending on someone’s inferred impulsivity and inhibitory control.

To create this approach, we conducted a driving study using a high-fidelity motion simulator to understand how cognitive factors affect people’s responses to driver safety interfaces. Our study revealed that the prototype interfaces had differing effects on drivers based on their level of impulsivity, as indicated by multiple self-reported and behavioral metrics. In particular, we observed that drivers with lower levels of impulsivity tended to slow down when exposed to the interfaces, while drivers with higher levels of impulsivity exhibited the opposite response. Indeed, previous research has shown that impulsive drivers are more likely to run yellow lights 71 , although yellow lights were designed to warn drivers that they may need to slow down. Our study is the first to show that vehicle safety interfaces may also lead to unintended driving behavior responses for some drivers based on their impulsivity.

Leveraging the data collected in the study, we trained an LSTM network that can infer cognitive traits and, based on these, decide whether or not to employ a driver safety interface. The results show that our decision-making scheme can infer latent factors that are compact, correlate with cognitive measures associated with impulsivity, and can be used effectively to select driver interfaces to improve driver behavior, resulting in lower speed at the zone of dilemma of yellow lights. Although previous work has shown the relationship between cognitive factors such as impulsivity and driving behavior, this is the first time a model is proposed and examined so as to make driver safety recommendations based on cognitive factor inferences conditioned on the driver’s behavior.

The suggested approach lends itself to fleet-scale, online, in-vehicle optimization of the interaction with the driver across the population. If deployed in such a manner, overall improvements in driver safety interfaces may lead to safer roads overall.

Data availability

Data and material will be made available upon request by emailing the corresponding authors.

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This work has been funded by Toyota Research Institute. All authors work for and receive compensation from Toyota Research Institute.

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These authors contributed equally: Emily S. Sumner, Jonathan DeCastro, Jean Costa, Deepak E. Gopinath, Everlyne Kimani, Tiffany Chen and Guy Rosman.

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Toyota Research Institute, Los Altos, CA, USA

Emily S. Sumner, Jonathan DeCastro, Jean Costa, Deepak E. Gopinath, Everlyne Kimani, Shabnam Hakimi, Allison Morgan, Andrew Best, Hieu Nguyen, Daniel J. Brooks, Bassam ul Haq, Andrew Patrikalakis, Hiroshi Yasuda, Kate Sieck, Avinash Balachandran, Tiffany L. Chen & Guy Rosman

Cambridge, MA, USA

Emily S. Sumner, Jonathan DeCastro, Deepak E. Gopinath, Daniel J. Brooks & Guy Rosman

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E.S., J.D., J.C., D.G., E.K., S.H., A.M., A.B., D.B., H.Y., K.S., T.L.C., A.B., and G.R. designed the research. E.S., J.D., J.C., E.G., E.K., A.M., A.B., H.N., D.B., and H.Y. performed the research. J.D., D.G., H.N., B.H., A.P., and D.B. designed analytic tools. J.D., D.G., J.C., and E.K. analyzed the data. E.S., J.D., J.C., D.G., E.K., A.M., H.Y., T.L.C. and G.R. wrote the paper. All authors reviewed the manuscript.

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Correspondence to Emily S. Sumner or Jonathan DeCastro .

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Sumner, E.S., DeCastro, J., Costa, J. et al. Personalizing driver safety interfaces via driver cognitive factors inference. Sci Rep 14 , 18058 (2024). https://doi.org/10.1038/s41598-024-65144-8

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Received : 18 January 2024

Accepted : 17 June 2024

Published : 05 August 2024

DOI : https://doi.org/10.1038/s41598-024-65144-8

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