Dual inheritance theory

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Dual_inheritance_theory

Dual inheritance theory (DIT), also known as gene–culture coevolution or biocultural evolution, was developed in the 1960s through early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution. Genes and culture continually interact in a feedback loop: changes in genes can lead to changes in culture which can then influence genetic selection, and vice versa. One of the theory's central claims is that culture evolves partly through a Darwinian selection process, which dual inheritance theorists often describe by analogy to genetic evolution.

'Culture', in this context is defined as 'socially learned behavior', and 'social learning' is defined as copying behaviors observed in others or acquiring behaviors through being taught by others. Most of the modelling done in the field relies on the first dynamic (copying) though it can be extended to teaching. Social learning at its simplest involves blind copying of behaviors from a model (someone observed behaving), though it is also understood to have many potential biases, including success bias (copying from those who are perceived to be better off), status bias (copying from those with higher status), homophily (copying from those most like ourselves), conformist bias (disproportionately picking up behaviors that more people are performing), etc. Understanding social learning is a system of pattern replication, and understanding that there are different rates of survival for different socially learned cultural variants, this sets up, by definition, an evolutionary structure: cultural evolution.

Because genetic evolution is relatively well understood, most of DIT examines cultural evolution and the interactions between cultural evolution and genetic evolution.

Theoretical basis

DIT holds that genetic and cultural evolution interacted in the evolution of Homo sapiens. DIT recognizes that the natural selection of genotypes is an important component of the evolution of human behavior and that cultural traits can be constrained by genetic imperatives. However, DIT also recognizes that genetic evolution has endowed the human species with a parallel evolutionary process of cultural evolution. DIT makes three main claims:

Culture capacities are adaptations

The human capacity to store and transmit culture arose from genetically evolved psychological mechanisms. This implies that at some point during the evolution of the human species a type of social learning leading to cumulative cultural evolution was evolutionarily advantageous.

Culture evolves

Social learning processes give rise to cultural evolution. Cultural traits are transmitted differently from genetic traits and, therefore, result in different population-level effects on behavioral variation.

Genes and culture co-evolve

Cultural traits alter the social and physical environments under which genetic selection operates. For example, the cultural adoptions of agriculture and dairying have, in humans, caused genetic selection for the traits to digest starch and lactose, respectively. As another example, it is likely that once culture became adaptive, genetic selection caused a refinement of the cognitive architecture that stores and transmits cultural information. This refinement may have further influenced the way culture is stored and the biases that govern its transmission.

DIT also predicts that, under certain situations, cultural evolution may select for traits that are genetically maladaptive. An example of this is the demographic transition, which describes the fall of birth rates within industrialized societies. Dual inheritance theorists hypothesize that the demographic transition may be a result of a prestige bias, where individuals that forgo reproduction to gain more influence in industrial societies are more likely to be chosen as cultural models.

View of culture

People have defined the word "culture" to describe a large set of different phenomena. A definition that sums up what is meant by "culture" in DIT is:

Culture is socially learned information stored in individuals' brains that is capable of affecting behavior.

This view of culture emphasizes population thinking by focusing on the process by which culture is generated and maintained. It also views culture as a dynamic property of individuals, as opposed to a view of culture as a superorganic entity to which individuals must conform. This view's main advantage is that it connects individual-level processes to population-level outcomes.

Genetic influence on cultural evolution

Genes affect cultural evolution via psychological predispositions on cultural learning. Genes encode much of the information needed to form the human brain. Genes constrain the brain's structure and, hence, the ability of the brain to acquire and store culture. Genes may also endow individuals with certain types of transmission bias (described below).

Cultural influences on genetic evolution

Culture can profoundly influence gene frequencies in a population.

Lactase persistence

One of the best known examples is the prevalence of the genotype for adult lactose absorption in human populations, such as Northern Europeans and some African societies, with a long history of raising cattle for milk. Until around 7,500 years ago, lactase production stopped shortly after weaning, and in societies which did not develop dairying, such as East Asians and Amerindians, this is still true today. In areas with lactase persistence, it is believed that by domesticating animals, a source of milk became available while an adult and thus strong selection for lactase persistence could occur, in a Scandinavian population the estimated selection coefficient was 0.09-0.19. This implies that the cultural practice of raising cattle first for meat and later for milk led to selection for genetic traits for lactose digestion. Recently, analysis of natural selection on the human genome suggests that civilization has accelerated genetic change in humans over the past 10,000 years.

Food processing

Culture has driven changes to the human digestive systems making many digestive organs, such as teeth or stomach, smaller than expected for primates of a similar size, and has been attributed to one of the reasons why humans have such large brains compared to other great apes. This is due to food processing. Early examples of food processing include pounding, marinating and most notably cooking. Pounding meat breaks down the muscle fibres, hence taking away some of the job from the mouth, teeth and jaw. Marinating emulates the action of the stomach with high acid levels. Cooking partially breaks down food making it more easily digestible. Food enters the body effectively partly digested, and as such food processing reduces the work that the digestive system has to do. This means that there is selection for smaller digestive organs as the tissue is energetically expensive, those with smaller digestive organs can process their food but at a lower energetic cost than those with larger organs. Cooking is notable because the energy available from food increases when cooked and this also means less time is spent looking for food.

Humans living on cooked diets spend only a fraction of their day chewing compared to other extant primates living on raw diets. American girls and boys spent on average 7 to 8 percent of their day chewing respectively (1.68 to 1.92 hours per day), compared to chimpanzees, who spend more than 6 hours a day chewing. This frees up time which can be used for hunting. A raw diet means hunting is constrained since time spent hunting is time not spent eating and chewing plant material, but cooking reduces the time required to get the day's energy requirements, allowing for more subsistence activities. Digestibility of cooked carbohydrates is approximately on average 30% higher than digestibility of non-cooked carbohydrates. This increased energy intake, more free time and savings made on tissue used in the digestive system allowed for the selection of genes for larger brain size.

Despite its benefits, brain tissue requires a large amount of calories, hence a main constraint in selection for larger brains is calorie intake. A greater calorie intake can support greater quantities of brain tissue. This is argued to explain why human brains can be much larger than other apes, since humans are the only ape to engage in food processing. The cooking of food has influenced genes to the extent that, research suggests, humans cannot live without cooking. A study on 513 individuals consuming long-term raw diets found that as the percentage of their diet which was made up of raw food and/or the length they had been on a diet of raw food increased, their BMI decreased. This is despite access to many non-thermal processing, like grinding, pounding or heating to 48 °C. (118 °F). With approximately 86 billion neurons in the human brain and 60–70 kg body mass, an exclusively raw diet close to that of what extant primates have would be not viable as, when modelled, it is argued that it would require an infeasible level of more than nine hours of feeding every day. However, this is contested, with alternative modelling showing enough calories could be obtained within 5–6 hours per day. Some scientists and anthropologists point to evidence that brain size in the Homo lineage started to increase well before the advent of cooking due to increased consumption of meat and that basic food processing (slicing) accounts for the size reduction in organs related to chewing. Cornélio et al. argues that improving cooperative abilities and a varying of diet to more meat and seeds improved foraging and hunting efficiency. It is this that allowed for the brain expansion, independent of cooking which they argue came much later, a consequence from the complex cognition that developed. Yet this is still an example of a cultural shift in diet and the resulting genetic evolution. Further criticism comes from the controversy of the archaeological evidence available. Some claim there is a lack of evidence of fire control when brain sizes first started expanding. Wrangham argues that anatomical evidence around the time of the origin of Homo erectus (1.8 million years ago), indicates that the control of fire and hence cooking occurred. At this time, the largest reductions in tooth size in the entirety of human evolution occurred, indicating that softer foods became prevalent in the diet. Also at this time was a narrowing of the pelvis indicating a smaller gut and also there is evidence that there was a loss of the ability to climb which Wrangham argues indicates the control of fire, since sleeping on the ground needs fire to ward off predators. The proposed increases in brain size from food processing will have led to a greater mental capacity for further cultural innovation in food processing which will have increased digestive efficiency further providing more energy for further gains in brain size. This positive feedback loop is argued to have led to the rapid brain size increases seen in the Homo lineage.

Mechanisms of cultural evolution

In DIT, the evolution and maintenance of cultures is described by five major mechanisms: natural selection of cultural variants, random variation, cultural drift, guided variation and transmission bias.

Natural selection

Cultural differences among individuals can lead to differential survival of individuals. The patterns of this selective process depend on transmission biases and can result in behavior that is more adaptive to a given environment.

Random variation

Random variation arises from errors in the learning, display or recall of cultural information, and is roughly analogous to the process of mutation in genetic evolution.

Cultural drift

Cultural drift is a process roughly analogous to genetic drift in evolutionary biology. In cultural drift, the frequency of cultural traits in a population may be subject to random fluctuations due to chance variations in which traits are observed and transmitted (sometimes called "sampling error"). These fluctuations might cause cultural variants to disappear from a population. This effect should be especially strong in small populations. A model by Hahn and Bentley shows that cultural drift gives a reasonably good approximation to changes in the popularity of American baby names. Drift processes have also been suggested to explain changes in archaeological pottery and technology patent applications. Changes in the songs of song birds are also thought to arise from drift processes, where distinct dialects in different groups occur due to errors in songbird singing and acquisition by successive generations. Cultural drift is also observed in an early computer model of cultural evolution.

Guided variation

Cultural traits may be gained in a population through the process of individual learning. Once an individual learns a novel trait, it can be transmitted to other members of the population. The process of guided variation depends on an adaptive standard that determines what cultural variants are learned.

Biased transmission

Understanding the different ways that culture traits can be transmitted between individuals has been an important part of DIT research since the 1970s. Transmission biases occur when some cultural variants are favored over others during the process of cultural transmission. Boyd and Richerson (1985) defined and analytically modeled a number of possible transmission biases. The list of biases has been refined over the years, especially by Henrich and McElreath.

Content bias

Content biases result from situations where some aspect of a cultural variant's content makes them more likely to be adopted. Content biases can result from genetic preferences, preferences determined by existing cultural traits, or a combination of the two. For example, food preferences can result from genetic preferences for sugary or fatty foods and socially-learned eating practices and taboos. Content biases are sometimes called "direct biases."

Context bias

Context biases result from individuals using clues about the social structure of their population to determine what cultural variants to adopt. This determination is made without reference to the content of the variant. There are two major categories of context biases: model-based biases, and frequency-dependent biases.

Model-based biases

Model-based biases result when an individual is biased to choose a particular "cultural model" to imitate. There are four major categories of model-based biases: prestige bias, skill bias, success bias, and similarity bias. A "prestige bias" results when individuals are more likely to imitate cultural models that are seen as having more prestige. A measure of prestige could be the amount of deference shown to a potential cultural model by other individuals. A "skill bias" results when individuals can directly observe different cultural models performing a learned skill and are more likely to imitate cultural models that perform better at the specific skill. A "success bias" results from individuals preferentially imitating cultural models that they determine are most generally successful (as opposed to successful at a specific skill as in the skill bias.) A "similarity bias" results when individuals are more likely to imitate cultural models that are perceived as being similar to the individual based on specific traits.

Frequency-dependent biases

Frequency-dependent biases result when an individual is biased to choose particular cultural variants based on their perceived frequency in the population. The most explored frequency-dependent bias is the "conformity bias." Conformity biases result when individuals attempt to copy the mean or the mode cultural variant in the population. Another possible frequency dependent bias is the "rarity bias." The rarity bias results when individuals preferentially choose cultural variants that are less common in the population. The rarity bias is also sometimes called a "nonconformist" or "anti-conformist" bias.

Social learning and cumulative cultural evolution

In DIT, the evolution of culture is dependent on the evolution of social learning. Analytic models show that social learning becomes evolutionarily beneficial when the environment changes with enough frequency that genetic inheritance can not track the changes, but not fast enough that individual learning is more efficient. For environments that have very little variability, social learning is not needed since genes can adapt fast enough to the changes that occur, and innate behaviour is able to deal with the constant environment. In fast changing environments cultural learning would not be useful because what the previous generation knew is now outdated and will provide no benefit in the changed environment, and hence individual learning is more beneficial. It is only in the moderately changing environment where cultural learning becomes useful since each generation shares a mostly similar environment but genes have insufficient time to change to changes in the environment. While other species have social learning, and thus some level of culture, only humans, some birds and chimpanzees are known to have cumulative culture. Boyd and Richerson argue that the evolution of cumulative culture depends on observational learning and is uncommon in other species because it is ineffective when it is rare in a population. They propose that the environmental changes occurring in the Pleistocene may have provided the right environmental conditions. Michael Tomasello argues that cumulative cultural evolution results from a ratchet effect that began when humans developed the cognitive architecture to understand others as mental agents. Furthermore, Tomasello proposed in the 80s that there are some disparities between the observational learning mechanisms found in humans and great apes - which go some way to explain the observable difference between great ape traditions and human types of culture (see Emulation (observational learning)).

Cultural group selection

Further information on cultural group selection: Cultural group selection

Although group selection is commonly thought to be nonexistent or unimportant in genetic evolution, DIT predicts that, due to the nature of cultural inheritance, it may be an important force in cultural evolution. Group selection occurs in cultural evolution because conformist biases make it difficult for novel cultural traits to spread through a population (see above section on transmission biases). Conformist bias also helps maintain variation between groups. These two properties, rare in genetic transmission, are necessary for group selection to operate. Based on an earlier model by Cavalli-Sforza and Feldman, Boyd and Richerson show that conformist biases are almost inevitable when traits spread through social learning, implying that group selection is common in cultural evolution. Analysis of small groups in New Guinea imply that cultural group selection might be a good explanation for slowly changing aspects of social structure, but not for rapidly changing fads. The ability of cultural evolution to maintain intergroup diversity is what allows for the study of cultural phylogenetics.

Historical development

In 1876, Friedrich Engels wrote a manuscript titled The Part Played by Labour in the Transition from Ape to Man, accredited as a founding document of DIH; “The approach to gene-culture coevolution first developed by Engels and developed later on by anthropologists…” is described by Stephen Jay Gould as “…the best nineteenth-century case for gene-culture coevolution.” The idea that human cultures undergo a similar evolutionary process as genetic evolution also goes back to Darwin. In the 1960s, Donald T. Campbell published some of the first theoretical work that adapted principles of evolutionary theory to the evolution of cultures. In 1976, two developments in cultural evolutionary theory set the stage for DIT. In that year Richard Dawkins's The Selfish Gene introduced ideas of cultural evolution to a popular audience. Although one of the best-selling science books of all time, because of its lack of mathematical rigor, it had little effect on the development of DIT. Also in 1976, geneticists Marcus Feldman and Luigi Luca Cavalli-Sforza published the first dynamic models of gene–culture coevolution. These models were to form the basis for subsequent work on DIT, heralded by the publication of three seminal books in the 1980s.

The first was Charles Lumsden and E.O. Wilson's Genes, Mind and Culture. This book outlined a series of mathematical models of how genetic evolution might favor the selection of cultural traits and how cultural traits might, in turn, affect the speed of genetic evolution. While it was the first book published describing how genes and culture might coevolve, it had relatively little effect on the further development of DIT. Some critics felt that their models depended too heavily on genetic mechanisms at the expense of cultural mechanisms. Controversy surrounding Wilson's sociobiological theories may also have decreased the lasting effect of this book.

The second 1981 book was Cavalli-Sforza and Feldman's Cultural Transmission and Evolution: A Quantitative Approach. Borrowing heavily from population genetics and epidemiology, this book built a mathematical theory concerning the spread of cultural traits. It describes the evolutionary implications of vertical transmission, passing cultural traits from parents to offspring; oblique transmission, passing cultural traits from any member of an older generation to a younger generation; and horizontal transmission, passing traits between members of the same population.

The next significant DIT publication was Robert Boyd and Peter Richerson's 1985 Culture and the Evolutionary Process. This book presents the now-standard mathematical models of the evolution of social learning under different environmental conditions, the population effects of social learning, various forces of selection on cultural learning rules, different forms of biased transmission and their population-level effects, and conflicts between cultural and genetic evolution. The book's conclusion also outlined areas for future research that are still relevant today.

Current and future research

In their 1985 book, Boyd and Richerson outlined an agenda for future DIT research. This agenda, outlined below, called for the development of both theoretical models and empirical research. DIT has since built a rich tradition of theoretical models over the past two decades. However, there has not been a comparable level of empirical work.

In a 2006 interview Harvard biologist E. O. Wilson expressed disappointment at the little attention afforded to DIT:

"...for some reason I haven't fully fathomed, this most promising frontier of scientific research has attracted very few people and very little effort."

Kevin Laland and Gillian Ruth Brown attribute this lack of attention to DIT's heavy reliance on formal modeling.

"In many ways the most complex and potentially rewarding of all approaches, [DIT], with its multiple processes and cerebral onslaught of sigmas and deltas, may appear too abstract to all but the most enthusiastic reader. Until such a time as the theoretical hieroglyphics can be translated into a respectable empirical science most observers will remain immune to its message."

Economist Herbert Gintis disagrees with this critique, citing empirical work as well as more recent work using techniques from behavioral economics. These behavioral economic techniques have been adapted to test predictions of cultural evolutionary models in laboratory settings as well as studying differences in cooperation in fifteen small-scale societies in the field.

Since one of the goals of DIT is to explain the distribution of human cultural traits, ethnographic and ethnologic techniques may also be useful for testing hypothesis stemming from DIT. Although findings from traditional ethnologic studies have been used to buttress DIT arguments, thus far there have been little ethnographic fieldwork designed to explicitly test these hypotheses.

Herb Gintis has named DIT one of the two major conceptual theories with potential for unifying the behavioral sciences, including economics, biology, anthropology, sociology, psychology and political science. Because it addresses both the genetic and cultural components of human inheritance, Gintis sees DIT models as providing the best explanations for the ultimate cause of human behavior and the best paradigm for integrating those disciplines with evolutionary theory. In a review of competing evolutionary perspectives on human behavior, Laland and Brown see DIT as the best candidate for uniting the other evolutionary perspectives under one theoretical umbrella.

Relation to other fields

Sociology and cultural anthropology

Two major topics of study in both sociology and cultural anthropology are human cultures and cultural variation. However, Dual Inheritance theorists charge that both disciplines too often treat culture as a static superorganic entity that dictates human behavior. Cultures are defined by a suite of common traits shared by a large group of people. DIT theorists argue that this doesn't sufficiently explain variation in cultural traits at the individual level. By contrast, DIT models human culture at the individual level and views culture as the result of a dynamic evolutionary process at the population level.

Human sociobiology and evolutionary psychology

Evolutionary psychologists study the evolved architecture of the human mind. They see it as composed of many different programs that process information, each with assumptions and procedures that were specialized by natural selection to solve a different adaptive problem faced by our hunter-gatherer ancestors (e.g., choosing mates, hunting, avoiding predators, cooperating, using aggression). These evolved programs contain content-rich assumptions about how the world and other people work. When ideas are passed from mind to mind, they are changed by these evolved inference systems (much like messages get changed in a game of telephone). But the changes are not usually random. Evolved programs add and subtract information, reshaping the ideas in ways that make them more "intuitive", more memorable, and more attention-grabbing. In other words, "memes" (ideas) are not precisely like genes. Genes are normally copied faithfully as they are replicated, but ideas normally are not. It's not just that ideas mutate every once in a while, like genes do. Ideas are transformed every time they are passed from mind to mind, because the sender's message is being interpreted by evolved inference systems in the receiver. It is useful for some applications to note, however, that there are ways to pass ideas which are more resilient and involve substantially less mutation, such as by mass distribution of printed media.

There is no necessary contradiction between evolutionary psychology and DIT, but evolutionary psychologists argue that the psychology implicit in many DIT models is too simple; evolved programs have a rich inferential structure not captured by the idea of a "content bias". They also argue that some of the phenomena DIT models attribute to cultural evolution are cases of "evoked culture"—situations in which different evolved programs are activated in different places, in response to cues in the environment.

Sociobiologists try to understand how maximizing genetic fitness, in either the modern era or past environments, can explain human behavior. When faced with a trait that seems maladaptive, some sociobiologists try to determine how the trait actually increases genetic fitness (maybe through kin selection or by speculating about early evolutionary environments). Dual inheritance theorists, in contrast, will consider a variety of genetic and cultural processes in addition to natural selection on genes.

Human behavioral ecology

Human behavioral ecology (HBE) and DIT have a similar relationship to what ecology and evolutionary biology have in the biological sciences. HBE is more concerned about ecological process and DIT more focused on historical process. One difference is that human behavioral ecologists often assume that culture is a system that produces the most adaptive outcome in a given environment. This implies that similar behavioral traditions should be found in similar environments. However, this is not always the case. A study of African cultures showed that cultural history was a better predictor of cultural traits than local ecological conditions.

Memetics

Memetics, which comes from the meme idea described in Dawkins's The Selfish Gene, is similar to DIT in that it treats culture as an evolutionary process that is distinct from genetic transmission. However, there are some philosophical differences between memetics and DIT. One difference is that memetics' focus is on the selection potential of discrete replicators (memes), where DIT allows for transmission of both non-replicators and non-discrete cultural variants. DIT does not assume that replicators are necessary for cumulative adaptive evolution. DIT also more strongly emphasizes the role of genetic inheritance in shaping the capacity for cultural evolution. But perhaps the biggest difference is a difference in academic lineage. Memetics as a label is more influential in popular culture than in academia. Critics of memetics argue that it is lacking in empirical support or is conceptually ill-founded, and question whether there is hope for the memetic research program succeeding. Proponents point out that many cultural traits are discrete, and that many existing models of cultural inheritance assume discrete cultural units, and hence involve memes.

Shortcomings and criticisms

Psychologist Liane Gabora has criticised DIT. She argues that use of the term ‘dual inheritance’ to refer to not just traits that are transmitted by way of a self-assembly code (as in genetic evolution) but also traits that are not transmitted by way of a self-assembly code (as in cultural evolution) is misleading, because this second use does not capture the algorithmic structure that makes an inheritance system require a particular kind of mathematical framework.

Other criticisms of the effort to frame culture in Darwinian terms have been leveled by Richard Lewontin, Niles Eldredge, and Stuart Kauffman.

Folk psychology

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Folk_psychology 

In philosophy of mind and cognitive science, folk psychology, or commonsense psychology, is a human capacity to explain and predict the behavior and mental state of other people. Processes and items encountered in daily life such as pain, pleasure, excitement, and anxiety use common linguistic terms as opposed to technical or scientific jargon. Folk psychology allows for an insight into social interactions and communication, thus stretching the importance of connection and how it is experienced.

Traditionally, the study of folk psychology has focused on how everyday people—those without formal training in the various academic fields of science—go about attributing mental states. This domain has primarily been centered on intentional states reflective of an individual's beliefs and desires; each described in terms of everyday language and concepts such as "beliefs", "desires", "fear", and "hope".

Belief and desire have been the main idea of folk psychology as both suggest the mental states we partake in. Belief comes from the mindset of how we take the world to be while desire comes from how we want the world to be. From both of these mindsets, our intensity of predicting others mental states can have different results. 

Key folk concepts

Intentionality

When perceiving, explaining, or criticizing human behaviour, people distinguish between intentional and unintentional actions. An evaluation of an action as stemming from purposeful action or accidental circumstances is one of the key determinants in social interaction. Others are the environmental conditions or pre-cognitive matters. For example, a critical remark that is judged to be intentional on the part of the receiver of the message can be viewed as a hurtful insult. Conversely, if considered unintentional, the same remark may be dismissed and forgiven.

The folk concept of intentionality is used in the legal system to distinguish between intentional and unintentional behavior.  When looking at an individual, there is an unconventional way of explaining behavior in law. By looking at behaviors and expressions, folk psychology is used to predict behaviors that have been acted out in the past.

The importance of this concept transcends almost all aspects of everyday life: with empirical studies in social and developmental psychology exploring perceived intentionality's role as a mediator for aggression, relationship conflict, judgements of responsibility blame or punishment.

Recent empirical literature on folk psychology has shown that people's theories regarding intentional actions involve four distinct factors: beliefs, desires, causal histories, and enabling factors. Here, beliefs and desires represent the central variables responsible for the folk theories of intention.

Desires embody outcomes that an individual seeks, including those that are impossible to achieve. The key difference between desires and intentions is that desires can be purely hypothetical, whereas intentions specify an outcome that the individual is actually trying to bring to fruition.

In terms of beliefs, there are several types that are relevant to intentions—outcome beliefs and ability beliefs. Outcome beliefs are beliefs as to whether a given action will fulfill an intention, as in "purchasing a new watch will impress my friends". Ability consists of an actor's conviction regarding his or her ability to perform an action, as in "I really can afford the new watch". In light of this, Heider postulated that ability beliefs could be attributed with causing individuals to form goals that would not otherwise have been entertained.

Comprehension and prediction

Context model

Folk psychology is crucial to evaluating and ultimately understanding novel concepts and items. Developed by Medin, Altom, and Murphy, the Context Model hypothesizes that as a result of mental models in the form of prototype and exemplar representations, individuals are able to more accurately represent and comprehend the environment around them.

According to the model, the overall similarity between the prototype and a given instance of a category is evaluated based on multiple dimensions (e.g., shape, size, color). A multiplicative function modeled after this phenomenon was created.

${\displaystyle s(P,E_i)=\prod _{k}s(P,E_{ik})}$

Here, ${\displaystyle s(P,E_i)}$ represents the similarity between the prototype and the ${\displaystyle i}$th exemplar, ${\displaystyle k}$ is the subscript for the dimensions ${\displaystyle (k=1,\dots ,K)}$, and ${\displaystyle s(P,E_{ik})}$ is the similarity between the prototype and the ${\displaystyle i}$th exemplar on the ${\displaystyle k}$th dimension.

Prediction model

There are other prediction models when it comes to the different cognitive thoughts an individual might have when trying to predict human behavior or human mental states. From Lewis, one platitude includes individuals casually expressing stimuli and behavior. The other platitude includes assuming a type of mental state another has. 

Consequence of prediction model

The prediction model has received some cautions as the idea of folk psychology has been apart of Lewis's ideas. Common statements about mental health have been considered in Lewis's prediction model, therefore there was an assumed lack of quality scientific research.

Explanation

Conversational Model

Given that folk psychology represents causal knowledge associated with the mind's categorization processes, it follows that folk psychology is actively employed in aiding the explanation of everyday actions. Denis Hilton's (1990) Conversational Model was created with this causal explanation in mind, with the model having the ability to generate specific predictions. Hilton coined his model the 'conversational' model because he argued that as a social activity, unlike prediction, explanation requires an audience: to whom the individual explains the event or action. According to the model, causal explanations follow two particular conversational maxims from Grice's (1975) models of conversation—the manner maxim and the quantity maxim. Grice indicated that the content of a conversation should be relevant, informative, and fitting of the audience's gap in knowledge. Cognizant of this, the Conversational Model indicates that the explainer, upon evaluation of his audience, will modify his explanation to cater their needs. In essence, demonstrating the inherent need for mental comparison and in subsequent modification of behaviour in everyday explanations.

Application and functioning

Belief–desire model

The belief–desire model of psychology illustrates one method in which folk psychology is utilized in everyday life. According to this model, people perform an action if they want an outcome and believe that it can be obtained by performing the action. However, beliefs and desires are not responsible for immediate action; intention acts as a mediator of belief/desire and action. In other words, consider a person who wants to achieve a goal, "G", and believes action "A" will aid in attaining "G"; this leads to an intention to perform "A", which is then carried out to produce action "A".

A schematic representation of folk psychology of belief, desire, intention, and action.

Schank & Abelson (1977) described this inclusion of typical beliefs, desires, and intentions underlying an action as akin to a "script" whereby an individual is merely following an unconscious framework that leads to the ultimate decision of whether an action will be performed. Similarly, Barsalou (1985) described the category of the mind as an "ideal" whereby if a desire, a belief, and an intention were all present, they would "rationally" lead to a given action. They coined this phenomenon the "ideal of rational action".

Goal-intentional action model

Existing literature has widely corroborated the fact that social behavior is greatly affected by the causes to which people attribute actions. In particular, it has been shown that an individual's interpretation of the causes of behavior reflects their pre-existing beliefs regarding the actor's mental state and motivation behind his or her actions. It follows that they draw on the assumed intentions of actors to guide their own responses to punish or reward the actor. This concept is extended to cover instances in which behavioral evidence is lacking. Under these circumstances, it has been shown that the individual will again draw on assumed intentions in order to predict the actions of the third party.

Although the two components are often used interchangeably in common parlance, there is an important distinction between the goals and intentions. This discrepancy lies in the fact that individuals with an intention to perform an action also foster the belief that it will be achieved, whereas the same person with a goal may not necessarily believe that the action is able to be performed in spite of having a strong desire to do so.

Predicting goals and actions, much like the Belief-Desire Model, involves moderating variables that determine whether an action will be performed. In the Goal-Intentional Action Model, the predictors of goals and actions are: the actors' beliefs about his or her abilities and their actual possession of preconditions required to carry out the action. Additionally, preconditions consist of the various conditions necessary in order for realization of intentions. This includes abilities and skills in addition to environmental variables that may come into play. Schank & Abelson raises the example of going to a restaurant, where the preconditions include the ability to afford the bill and get to the correct venue, in addition to the fact that the restaurant must be open for business. Traditionally, people prefer to allude to preconditions to explain actions that have a high probability of being unattainable, whereas goals tend to be described as a wide range of common actions.

Model of everyday inferences

Models of everyday inferences capture folk psychology of human informal reasoning. Many models of this nature have been developed. They express and refine our folk psychological ways of understanding of how one makes inferences.

For example, one model describes human everyday reasoning as combinations of simple, direct rules and similarity-based processes. From the interaction of these simple mechanisms, seemingly complex patterns of reasoning emerge. The model has been used to account for a variety of reasoning data.

Controversy

Further information: Eliminative materialism

Folk psychology remains the subject of much contention in academic circles with respect to its scope, method and the significance of its contributions to the scientific community. A large part of this criticism stems from the prevailing impression that folk psychology is a primitive practice reserved for the uneducated and non-academics in discussing their everyday lives.

There is significant debate over whether folk psychology is useful for academic purposes; specifically, whether it can be relevant with regard to the scientific psychology domain. It has been argued that a mechanism used for laypeople's understanding, predicting, and explaining each other's actions is inapplicable with regards to the requirements of the scientific method. Conversely, opponents have called for patience, seeing the mechanism employed by laypeople for understanding each other's actions as important in their formation of bases for future action when encountering similar situations. Malle & Knobe hailed this systematization of people's everyday understanding of the mind as an inevitable progression towards a more comprehensive field of psychology. Medin et al. provide another advantage of conceptualizing folk psychology with their Mixture Model of Categorization: it is advantageous as it helps predict action.

Human behavior

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Human_behavior

Social interaction and creative expression are forms of human behavior

Human behavior is the potential and expressed capacity (mentally, physically, and socially) of human individuals or groups to respond to internal and external stimuli throughout their life. Behavior is driven by genetic and environmental factors that affect an individual. Behavior is also driven, in part, by thoughts and feelings, which provide insight into individual psyche, revealing such things as attitudes and values. Human behavior is shaped by psychological traits, as personality types vary from person to person, producing different actions and behavior.

Social behavior accounts for actions directed at others. It is concerned with the considerable influence of social interaction and culture, as well as ethics, interpersonal relationships, politics, and conflict. Some behaviors are common while others are unusual. The acceptability of behavior depends upon social norms and is regulated by various means of social control. Social norms also condition behavior, whereby humans are pressured into following certain rules and displaying certain behaviors that are deemed acceptable or unacceptable depending on the given society or culture.

Cognitive behavior accounts for actions of obtaining and using knowledge. It is concerned with how information is learned and passed on, as well as creative application of knowledge and personal beliefs such as religion. Physiological behavior accounts for actions to maintain the body. It is concerned with basic bodily functions as well as measures taken to maintain health. Economic behavior accounts for actions regarding the development, organization, and use of materials as well as other forms of work. Ecological behavior accounts for actions involving the ecosystem. It is concerned with how humans interact with other organisms and how the environment shapes human behavior.

Study

Main article: Human ethology

Human behavior is studied by the social sciences, which include psychology, sociology, ethology, and their various branches and schools of thought. There are many different facets of human behavior, and no one definition or field study encompasses it in its entirety. The nature versus nurture debate is one of the fundamental divisions in the study of human behavior; this debate considers whether behavior is predominantly affected by genetic or environmental factors. The study of human behavior sometimes receives public attention due to its intersection with cultural issues, including crime, sexuality, and social inequality.

Some natural sciences also place emphasis on human behavior. Neurology and evolutionary biology, study how behavior is controlled by the nervous system and how the human mind evolved, respectively. In other fields, human behavior may be a secondary subject of study when considering how it affects another subject. Outside of formal scientific inquiry, human behavior and the human condition is also a major focus of philosophy and literature. Philosophy of mind considers aspects such as free will, the mind–body problem, and malleability of human behavior.

Human behavior may be evaluated through questionnaires, interviews, and experimental methods. Animal testing may also be used to test behaviors that can then be compared to human behavior. Twin studies are a common method by which human behavior is studied. Twins with identical genomes can be compared to isolate genetic and environmental factors in behavior. Lifestyle, susceptibility to disease, and unhealthy behaviors have been identified to have both genetic and environmental indicators through twin studies.

Social behavior

Further information: Sociology

Women bowing in Japan (c. 1880)

Human social behavior is the behavior that considers other humans, including communication and cooperation. It is highly complex and structured, based on advanced theory of mind that allows humans to attribute thoughts and actions to one another. Through social behavior, humans have developed society and culture distinct from other animals. Human social behavior is governed by a combination of biological factors that affect all humans and cultural factors that change depending on upbringing and societal norms. Human communication is based heavily on language, typically through speech or writing. Nonverbal communication and paralanguage can modify the meaning of communications by demonstrating ideas and intent through physical and vocal behaviors.

Social norms

Human behavior in a society is governed by social norms. Social norms are unwritten expectations that members of society have for one another. These norms are ingrained in the particular culture that they emerge from, and humans often follow them unconsciously or without deliberation. These norms affect every aspect of life in human society, including decorum, social responsibility, property rights, contractual agreement, morality, justice, and meaning. Many norms facilitate coordination between members of society and prove mutually beneficial, such as norms regarding communication and agreements. Norms are enforced by social pressure, and individuals that violate social norms risk social exclusion.

Systems of ethics are used to guide human behavior to determine what is moral. Humans are distinct from other animals in the use of ethical systems to determine behavior. Ethical behavior is human behavior that takes into consideration how actions will affect others and whether behaviors will be optimal for others. What constitutes ethical behavior is determined by the individual value judgments of the person and the collective social norms regarding right and wrong. Value judgments are intrinsic to people of all cultures, though the specific systems used to evaluate them may vary. These systems may be derived from divine law, natural law, civil authority, reason, or a combination of these and other principles. Altruism is an associated behavior in which humans consider the welfare of others equally or preferentially to their own. While other animals engage in biological altruism, ethical altruism is unique to humans.

Deviance is behavior that violates social norms. As social norms vary between individuals and cultures, the nature and severity of a deviant act is subjective. What is considered deviant by a society may also change over time as new social norms are developed. Deviance is punished by other individuals through social stigma, censure, or violence. Many deviant actions are recognized as crimes and punished through a system of criminal justice. Deviant actions may be punished to prevent harm to others, to maintain a particular worldview and way of life, or to enforce principles of morality and decency. Cultures also attribute positive or negative value to certain physical traits, causing individuals that do not have desirable traits to be seen as deviant.

Interpersonal relationships

Main article: Interpersonal relationship

A family in Noatak, Alaska (1929)

Interpersonal relationships can be evaluated by the specific choices and emotions between two individuals, or they can be evaluated by the broader societal context of how such a relationship is expected to function. Relationships are developed through communication, which creates intimacy, expresses emotions, and develops identity. An individual's interpersonal relationships form a social group in which individuals all communicate and socialize with one another, and these social groups are connected by additional relationships. Human social behavior is affected not only by individual relationships, but also by how behaviors in one relationship may affect others. Individuals that actively seek out social interactions are extraverts, and those that do not are introverts.

Romantic love is a significant interpersonal attraction toward another. Its nature varies by culture, but it is often contingent on gender, occurring in conjunction with sexual attraction and being either heterosexual or homosexual. It takes different forms and is associated with many individual emotions. Many cultures place a higher emphasis on romantic love than other forms of interpersonal attraction. Marriage is a union between two people, though whether it is associated with romantic love is dependent on the culture. Individuals that are closely related by consanguinity form a family. There are many variations on family structures that may include parents and children as well as stepchildren or extended relatives. Family units with children emphasize parenting, in which parents engage in a high level of parental investment to protect and instruct children as they develop over a period of time longer than that of most other mammals.

Politics and conflict

Further information: Political science, Theories of political behavior, and Conflict (process)

A depiction of men fighting in the First Battle of Komárom (1849)

When humans make decisions as a group, they engage in politics. Humans have evolved to engage in behaviors of self-interest, but this also includes behaviors that facilitate cooperation rather than conflict in collective settings. Individuals will often form in-group and out-group perceptions, through which individuals cooperate with the in-group and compete with the out-group. This causes behaviors such as unconsciously conforming, passively obeying authority, taking pleasure in the misfortune of opponents, initiating hostility toward out-group members, artificially creating out-groups when none exist, and punishing those that do not comply with the standards of the in-group. These behaviors lead to the creation of political systems that enforce in-group standards and norms.

When humans oppose one another, it creates conflict. It may occur when the involved parties have a disagreement of opinion, when one party obstructs the goals of another, or when parties experience negative emotions such as anger toward one another. Conflicts purely of disagreement are often resolved through communication or negotiation, but incorporation of emotional or obstructive aspects can escalate conflict. Interpersonal conflict is that between specific individuals or groups of individuals. Social conflict is that between different social groups or demographics. This form of conflict often takes place when groups in society are marginalized, do not have the resources they desire, wish to instigate social change, or wish to resist social change. Significant social conflict can cause civil disorder. International conflict is that between nations or governments. It may be solved through diplomacy or war.

Cognitive behavior

Main article: Cognition

People being taught to paint in Volgograd, Russia (2013)

Human cognition is distinct from that of other animals. This is derived from biological traits of human cognition, but also from shared knowledge and development passed down culturally. Humans are able to learn from one another due to advanced theory of mind that allows knowledge to be obtained through education. The use of language allows humans to directly pass knowledge to one another. The human brain has neuroplasticity, allowing it to modify its features in response to new experiences. This facilitates learning in humans and leads to behaviors of practice, allowing the development of new skills in individual humans. Behavior carried out over time can be ingrained as a habit, where humans will continue to regularly engage in the behavior without consciously deciding to do so.

Humans engage in reason to make inferences with a limited amount of information. Most human reasoning is done automatically without conscious effort on the part of the individual. Reasoning is carried out by making generalizations from past experiences and applying them to new circumstances. Learned knowledge is acquired to make more accurate inferences about the subject. Deductive reasoning infers conclusions that are true based on logical premises, while inductive reasoning infers what conclusions are likely to be true based on context.

Emotion is a cognitive experience innate to humans. Basic emotions such as joy, distress, anger, fear, surprise, and disgust are common to all cultures, though social norms regarding the expression of emotion may vary. Other emotions come from higher cognition, such as love, guilt, shame, embarrassment, pride, envy, and jealousy. These emotions develop over time rather than instantly and are more strongly influenced by cultural factors. Emotions are influenced by sensory information, such as color and music, and moods of happiness and sadness. Humans typically maintain a standard level of happiness or sadness determined by health and social relationships, though positive and negative events have short-term influences on mood. Humans often seek to improve the moods of one another through consolation, entertainment, and venting. Humans can also self-regulate mood through exercise and meditation.

Creativity is the use of previous ideas or resources to produce something original. It allows for innovation, adaptation to change, learning new information, and novel problem solving. Expression of creativity also supports quality of life. Creativity includes personal creativity, in which a person presents new ideas authentically, but it can also be expanded to social creativity, in which a community or society produces and recognizes ideas collectively. Creativity is applied in typical human life to solve problems as they occur. It also leads humans to carry out art and science. Individuals engaging in advanced creative work typically have specialized knowledge in that field, and humans draw on this knowledge to develop novel ideas. In art, creativity is used to develop new artistic works, such as visual art or music. In science, those with knowledge in a particular scientific field can use trial and error to develop theories that more accurately explain phenomena.

Religious behavior is a set of traditions that are followed based on the teachings of a religious belief system. The nature of religious behavior varies depending on the specific religious traditions. Most religious traditions involve variations of telling myths, practicing rituals, making certain things taboo, adopting symbolism, determining morality, experiencing altered states of consciousness, and believing in supernatural beings. Religious behavior is often demanding and has high time, energy, and material costs, and it conflicts with rational choice models of human behavior, though it does provide community-related benefits. Anthropologists offer competing theories as to why humans adopted religious behavior. Religious behavior is heavily influenced by social factors, and group involvement is significant in the development of an individual's religious behavior. Social structures such as religious organizations or family units allow the sharing and coordination of religious behavior. These social connections reinforce the cognitive behaviors associated with religion, encouraging orthodoxy and commitment. According to a Pew Research Center report, 54% of adults around the world state that religion is very important in their lives as of 2018.

Physiological behavior

See also: Psychophysiology

A boy eating in Harare, Zimbabwe (2017)

Humans undergo many behaviors common to animals to support the processes of the human body. Humans eat food to obtain nutrition. These foods may be chosen for their nutritional value, but they may also be eaten for pleasure. Eating often follows a food preparation process to make it more enjoyable. Humans dispose of excess food through waste. Excrement is often treated as taboo, particularly in developed and urban communities where sanitation is more widely available and excrement has no value as fertilizer. Humans also regularly engage in sleep, based on homeostatic and circadian factors. The circadian rhythm causes humans to require sleep at a regular pattern and is typically calibrated to the day-night cycle and sleep-wake habits. Homeostasis is also be maintained, causing longer sleep longer after periods of sleep deprivation. The human sleep cycle takes place over 90 minutes, and it repeats 3–5 times during normal sleep.

There are also unique behaviors that humans undergo to maintain physical health. Humans have developed medicine to prevent and treat illnesses. In industrialized nations, eating habits that favor better nutrition, hygienic behaviors that promote sanitation, medical treatment to eradicate diseases, and the use of birth control significantly improve human health. Humans can also engage in exercise beyond that required for survival to maintain health. Humans engage in hygiene to limit exposure to dirt and pathogens. Some of these behaviors are adaptive while others are learned. Basic behaviors of disgust evolved as an adaptation to prevent contact with sources of pathogens, resulting in a biological aversion to feces, body fluids, rotten food, and animals that are commonly disease vectors. Personal grooming, disposal of human corpses, use of sewerage, and use of cleaning agents are hygienic behaviors common to most human societies.

Humans reproduce sexually, engaging in sexual intercourse for both reproduction and sexual pleasure. Human reproduction is closely associated with human sexuality and an instinctive desire to procreate, though humans are unique in that they intentionally control the number of offspring that they produce. Humans engage in a large variety of reproductive behaviors relative to other animals, with various mating structures that include forms of monogamy, polygyny, and polyandry. How humans engage in mating behavior is heavily influenced by cultural norms and customs. Unlike most mammals, human women ovulate spontaneously rather than seasonally, with a menstrual cycle that typically lasts 25–35 days.

Humans are bipedal and move by walking. Human walking corresponds to the bipedal gait cycle, which involves alternating heel contact and toe off with the ground and slight elevation and rotation of the pelvis. Balance while walking learned during the first 7–9 years of life, and individual humans develop unique gaits while learning to displace weight, adjust center of mass, and correspond neural control with movement. Humans can achieve higher speed by running. The endurance running hypothesis proposes that humans can outpace most other animals over long distances through running, though human running causes a higher rate of energy exertion. The human body self-regulates through perspiration during periods of exertion, allowing humans more endurance than other animals. The human hand is prehensile and capable of grasping objects and applying force with control over the hand's dexterity and grip strength. This allows the use of complex tools by humans.

Economic behavior

Further information: Behavioral economics

Humans engage in predictable behaviors when considering economic decisions, and these behaviors may or may not be rational. Like all animals, humans make basic decisions through cost–benefit analysis and the risk–return spectrum, though humans are able to contemplate these decisions more thoroughly. Human economic decision making is often reference dependent, in which options are weighed in reference to the status quo rather than absolute gains and losses. Humans are also loss averse, fearing loss rather than seeking gain. Advanced economic behavior developed in humans after the Neolithic Revolution and the development of agriculture. These developments led to a sustainable supply of resources that allowed specialization in more complex societies.

Work

Main article: Work (human activity)

Women tending to farm animals in Mangskogs, Sweden (1911)

The nature of human work is defined by the complexity of society. The simplest societies are tribes that work primarily for sustenance as hunter-gatherers. In this sense, work is not a distinct activity but a constant that makes up all parts of life, as all members of the society must work consistently to stay alive. More advanced societies developed after the Neolithic Revolution, emphasizing work in agricultural and pastoral settings. In these societies, production is increased, ending the need for constant work and allowing some individuals to specialize and work in areas outside of food-production. This also created non-laborious work, as increasing occupational complexity required some individuals to specialize in technical knowledge and administration. Laborious work in these societies has variously been carried out by slaves, serfs, peasants, and guild craftsmen. The nature of work changed significantly during the Industrial Revolution in which the factory system was developed for use by industrializing nations. In addition to further increasing general quality of life, this development changed the dynamic of work. Under the factory system, workers increasingly collaborate with others, employers serve as authority figures during work hours, and forced labor is largely eradicated. Further changes occur in post-industrial societies where technological advance makes industries obsolete, replacing them with mass production and service industries.

Humans approach work differently based on both physical and personal attributes, and some work with more effectiveness and commitment than others. Some find work to contribute to personal fulfillment, while others work only out of necessity. Work can also serve as an identity, with individuals identifying themselves based on their occupation. Work motivation is complex, both contributing to and subtracting from various human needs. The primary motivation for work is for material gain, which takes the form of money in modern societies. It may also serve to create self-esteem and personal worth, provide activity, gain respect, and express creativity. Modern work is typically categorized as laborious or blue-collar work and non-laborious or white-collar work.

Leisure

Main article: Leisure

Men playing association football in Kilkenny, Ireland (2007)

Leisure is activity or lack of activity that takes place outside of work. It provides relaxation, entertainment, and improved quality of life for individuals. Engaging in leisure can be beneficial for physical and mental health. It may be used to seek temporary relief from psychological stress, to produce positive emotions, or to facilitate social interaction. Leisure can also facilitate health risks and negative emotions caused by boredom, substance abuse, or high-risk behavior.

Leisure may be defined as serious or casual. Serious leisure behaviors involve non-professional pursuit of arts and sciences, the development of hobbies, or career volunteering in an area of expertise. Casual leisure behaviors provide short-term gratification, but they do not provide long-term gratification or personal identity. These include play, relaxation, casual social interaction, volunteering, passive entertainment, active entertainment, and sensory stimulation. Passive entertainment is typically derived from mass media, which may include written works or digital media. Active entertainment involves games in which individuals participate. Sensory stimulation is immediate gratification from behaviors such as eating or sexual intercourse.

Consumption

Main article: Consumer behaviour

Humans operate as consumers that obtain and use goods. All production is ultimately designed for consumption, and consumers adapt their behavior based on the availability of production. Mass consumption began during the Industrial Revolution, caused by the development of new technologies that allowed for increased production. Many factors affect a consumer's decision to purchase goods through trade. They may consider the nature of the product, its associated cost, the convenience of purchase, and the nature of advertising around the product. Cultural factors may influence this decision, as different cultures value different things, and subcultures within these cultures may have distinct priorities as buyers. Social class, including wealth, education, and occupation may affect one's purchasing behavior. A consumer's interpersonal relationships and reference groups may also influence purchasing behavior.

Ecological behavior

Main article: Human ecology

A girl with lambs in Gilandeh, Iran (2018)

Like all living things, humans live in ecosystems and interact with other organisms. Human behavior is affected by the environment in which a human lives, and environments are affected by human habitation. Humans have also developed man-made ecosystems such as urban areas and agricultural land. Geography and landscape ecology determine how humans are distributed within an ecosystem, both naturally and through planned urban morphology.

Humans exercise control over the animals that live within their environment. Domesticated animals are trained and cared for by humans. Humans can develop social and emotional bonds with animals in their care. Pets are kept for companionship within human homes, including dogs and cats that have been bred for domestication over many centuries. Livestock animals, such as cattle, sheep, goats, and poultry, are kept on agricultural land to produce animal products. Domesticated animals are also kept in laboratories for animal testing. Non-domesticated animals are sometimes kept in nature reserves and zoos for tourism and conservation.

Causes and factors

Human behavior is influenced by biological and cultural elements. The structure and agency debate considers whether human behavior is predominantly led by individual human impulses or by external structural forces. Behavioral genetics considers how human behavior is affected by inherited traits. Though genes do not guarantee certain behaviors, certain traits can be inherited that make individuals more likely to engage in certain behaviors or express certain personalities. An individual's environment can also affect behavior, often in conjunction with genetic factors. An individual's personality and attitudes affect how behaviors are expressed, formed in conjunction by genetic and environmental factors.

Age

Further information: Ageing

An infant engaging in play in Los Angeles, California (2015)

Infants are limited in their ability to interpret their surroundings shortly after birth. Object permanence and understanding of motion typically develop within the first six months of an infant's life, though the specific cognitive processes are not understood. The ability to mentally categorize different concepts and objects that they perceive also develops within the first year. Infants are quickly able to discern their body from their surroundings and often take interest in their own limbs or actions they cause by two months of age. Infants practice imitation of other individuals to engage socially and learn new behaviors. In young infants, this involves imitating facial expressions, and imitation of tool use takes place within the first year. Communication develops over the first year, and infants begin using gestures to communicate intention around nine to ten months of age. Verbal communication develops more gradually, taking form during the second year of age.

Children develop fine motor skills shortly after infancy, in the range of three to six years of age, allowing them to engage in behaviors using the hands and eye–hand coordination and perform basic activities of self sufficiency. Children begin expressing more complex emotions in the three- to six-year-old range, including humor, empathy, and altruism, as well engaging in creativity and inquiry. Aggressive behaviors also become varied at this age as children engage in increased physical aggression before learning to favor diplomacy over aggression. Children at this age can express themselves using language with basic grammar. As children grow older, they develop emotional intelligence. Young children engage in basic social behaviors with peers, typically forming friendships centered on play with individuals of the same age and gender. Behaviors of young children are centered around play, which allows them to practice physical, cognitive, and social behaviors. Basic self-concept first develops as children grow, particularly centered around traits such as gender and ethnicity, and behavior is heavily affected by peers for the first time.

Adolescents undergo changes in behavior caused by puberty and the associated changes in hormone production. Production of testosterone increases sensation seeking and sensitivity to rewards in adolescents as well as aggression and risk-taking in adolescent boys. Production of estradiol causes similar risk-taking behavior among adolescent girls. The new hormones cause changes in emotional processing that allow for close friendships, stronger motivations and intentions, and adolescent sexuality. Adolescents undergo social changes on a large scale, developing a full self-concept and making autonomous decisions independently of adults. They typically become more aware of social norms and social cues than children, causing an increase in self-consciousness and adolescent egocentrism that guides behavior in social settings throughout adolescence.

Culture and environment

Human brains, as with those of all mammals, are neuroplastic. This means that the structure of the brain changes over time as neural pathways are altered in response to the environment. Many behaviors are learned through interaction with others during early development of the brain. Human behavior is distinct from the behavior of other animals in that it is heavily influenced by culture and language. Social learning allows humans to develop new behaviors by following the example of others. Culture is also the guiding influence that defines social norms.

Genetics

Physiology

Neurotransmitters, hormones, and metabolism are all recognized as biological factors in human behavior.

Physical disabilities can prevent individuals from engaging in typical human behavior or necessitate alternative behaviors. Accommodations and accessibility are often made available for individuals with physical disabilities in developed nations, including health care, assistive technology, and vocational services. Severe disabilities are associated with increased leisure time but also with a lower satisfaction in the quality of leisure time. Productivity and health both commonly undergo long term decline following the onset of a severe disability. Mental disabilities are those that directly affect cognitive and social behavior. Common mental disorders include mood disorders, anxiety disorders, personality disorders, and substance dependence.