Foundational areas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise from evolutionary theory itself: survival, mating, parenting, family and kinship, interactions with non-kin, and cultural evolution.
Survival and individual-level psychological adaptations Problems of survival are clear targets for the evolution of physical and psychological adaptations. Major problems the ancestors of present-day humans faced included food selection and acquisition; territory selection and physical shelter; and avoiding predators and other environmental threats.
Consciousness Consciousness meets
George Williams' criteria of species universality, complexity, and functionality, and it is a
trait that apparently increases fitness. In his paper "Evolution of consciousness,"
John Eccles argues that special anatomical and physical adaptations of the mammalian
cerebral cortex gave rise to consciousness. In contrast, others have argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in pre-mammalian species because it improves the capacity for interaction with both social and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine. Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined by
Bernard J. Baars.
Richard Dawkins suggested that humans evolved consciousness in order to make themselves the subjects of thought. Daniel Povinelli suggests that large, tree-climbing
apes evolved consciousness to account for their own mass when moving safely among tree branches. Consistent with this hypothesis,
Gordon Gallup found that
chimpanzees and
orangutans, but not little monkeys or terrestrial
gorillas, demonstrated self-awareness in mirror tests. The concept of consciousness can refer to voluntary action, awareness, or wakefulness. However, even voluntary behavior involves unconscious mechanisms. Many cognitive processes take place in the cognitive unconscious, unavailable to conscious awareness. Some behaviors are conscious when learned but then become unconscious, seemingly automatic. Learning, especially implicitly learning a skill, can take place seemingly outside of consciousness. For example, plenty of people know how to turn right when they ride a bike, but very few can accurately explain how they actually do so. Evolutionary psychology views self-deception as an adaptation that can improve one's results in social exchanges. Sleep may have evolved to conserve energy when activity would be less fruitful or more dangerous, such as at night, and especially during the winter season.
Sensation and perception Many experts, such as
Jerry Fodor, write that the purpose of perception is knowledge, but evolutionary psychologists hold that its primary purpose is to guide action. For example, they say,
depth perception seems to have evolved not to help us know the distances to other objects but rather to help us move around in space. Evolutionary psychologists say that animals from fiddler crabs to humans use eyesight for collision avoidance, suggesting that vision is basically for directing action, not providing knowledge. Building and maintaining sense organs is metabolically expensive, so these organs evolve only when they improve an organism's fitness. More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one's metabolic resources, so the senses must provide exceptional benefits to fitness. Perception accurately mirrors the world; animals get useful, accurate information through their senses. Scientists who study perception and sensation have long understood the human senses as adaptations to their surrounding worlds. Depth perception involves of processing over half a dozen visual cues, each of which is based on a regularity of the physical world. Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and passes through objects. Sound waves go around corners and interact with obstacles, creating a complex pattern that includes useful information about the sources of and distances to objects. Larger animals naturally make lower-pitched sounds as a consequence of their size. The range over which an animal hears, on the other hand, is determined by adaptation. Homing pigeons, for example, can hear the very low-pitched sound (infrasound) that carries great distances, even though most smaller animals detect higher-pitched sounds. Taste and smell respond to chemicals in the environment that are thought to have been significant for fitness in the environment of evolutionary adaptation. For example, salt and sugar were apparently both valuable to the human or pre-human inhabitants of the environment of evolutionary adaptations, so present-day humans have an intrinsic hunger for salty and sweet tastes. The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain. Pain, while unpleasant, is adaptive. An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation. For example, one's eyes automatically adjust to dim or bright ambient light. Sensory abilities of different organisms often coevolve, as is the case with the hearing of echolocating bats and that of the moths that have evolved to respond to the sounds that the bats make. Evolutionary psychologists contend that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks. For example, people with damage to a particular part of the brain have the specific defect of not being able to recognize faces (prosopagnosia). Evolutionary psychology suggests that this indicates a so-called face-reading module.
Learning and facultative adaptations In evolutionary psychology, learning is said to be accomplished through evolved capacities, specifically facultative adaptations. Facultative adaptations manifest differently in response to environmental input. Sometimes input comes during development and helps shape it. For example, migrating birds learn to orient themselves by the stars during a
critical period in their maturation. Evolutionary psychologists believe that humans also learn language along an evolved program, with critical periods. The input can also come during daily tasks, helping the organism cope with changing environmental conditions. For example, animals evolved
Pavlovian conditioning to solve problems involving causal relationships. Animals learn most easily when those tasks resemble problems that they faced in their evolutionary past, such as a rat learning where to find food or water. Learning capacities sometimes demonstrate differences between the sexes. In many animal species, for example, males can solve spatial problems faster and more accurately than females, due to the effects of male hormones during development. The same might be true of humans.
Emotion and motivation Motivations direct and energize behavior, while emotions provide the affective component to motivation, positive or negative. In the early 1970s,
Paul Ekman and colleagues began a line of research that suggests that many emotions are universal. He found evidence that humans share at least five basic emotions: fear, sadness, happiness, anger, and disgust. Social emotions evidently evolved to motivate social behaviors that were adaptive in the environment of evolutionary adaptation. For example, spite seems to work against the individual, but it can establish an individual's reputation as someone to be feared. Shame and pride can motivate behaviors that help one maintain one's standing in a community, and self-esteem is one's estimate of one's status. Motivation has a neurobiological basis in the brain's
reward system. Recently, it has been suggested that reward systems may evolve in such a way that there may be an
inherent or unavoidable
trade-off in the motivational system for activities of short versus long duration.
Cognition Cognition refers to internal representations of the world and internal information processing. From an evolutionary psychology perspective, cognition is not "general purpose". Cognition uses heuristics, or strategies, that generally increase the likelihood of solving problems that the ancestors of present-day humans routinely faced. For example, present-day humans are far more likely to solve a logic problem that involves detecting cheating (a common problem given humans' social nature) than the same problem presented in purely abstract terms. Since the ancestors of present-day humans did not encounter truly random events and lived under simpler life conditions, present-day humans may be cognitively predisposed to misperceive patterns in random sequences.
Gambler's fallacy is one example of this. Gamblers may falsely believe that they have hit a
lucky streak even when each outcome is actually random and independent of previous trials. Many people assume that a coin flip sequence of nine Heads makes Tails more probable on the tenth try. Humans find it far easier to make diagnoses or predictions using frequency data than when the same information is presented as probabilities or percentages. Perhaps these evaluations are connected to ancient human groups residing in small tribes (typically fewer than 150 individuals), where frequency data was more prevalent and unexpected events were less common.
Personality Evolutionary psychology is primarily interested in identifying commonalities between people, or the basic human psychological nature. From an evolutionary perspective, the fact that people have fundamental differences in personality traits initially presents something of a puzzle. Personality traits are conceptualized by evolutionary psychologists as arising from normal variation around an optimum, due to frequency-dependent selection (behavioral
polymorphisms), or as facultative adaptations. Like variability in height, some personality traits may simply reflect inter-individual variability around a general optimum. Or, personality traits may represent different genetically predisposed "behavioral morphs" – alternate behavioral strategies that depend on the frequency of competing behavioral strategies in the population. For example, if most of the population is generally trusting and gullible, the behavioral morph of being a "cheater" (or, in the extreme case, a sociopath) may be advantageous. Finally, like many other psychological adaptations, personality traits may be facultative – sensitive to typical variations in the social environment, especially during early development. For example, later-born children are more likely than firstborns to be rebellious, less conscientious, and more open to new experiences, which may be advantageous to them given their particular niche in family structure. Shared environmental influences do play a role in personality and are not always of less importance than genetic factors. However, shared environmental influences often decrease to near zero after adolescence but do not completely disappear.
Language According to
Steven Pinker, who builds on the work by
Noam Chomsky, the universal human ability to learn to talk between the ages of 1-4, basically without training, suggests that language acquisition is a distinctly human psychological adaptation. Pinker and
Bloom argue that language as a mental faculty shares many likenesses with the complex organs of the body, which suggests that, like these organs, language has evolved as an adaptation, since this is the only known mechanism by which such complex organs can develop. Pinker follows Chomsky in arguing that the fact that children can learn any human language with no explicit instruction suggests that language, including most of grammar, is basically innate and that it only needs to be activated by interaction. Chomsky himself does not believe language to have evolved as an adaptation, but suggests that it likely evolved as a byproduct of some other adaptation, a so-called
spandrel. But Pinker and Bloom argue that the organic nature of language strongly suggests an adaptive origin. Evolutionary psychologists hold that the
FOXP2 gene may well be associated with the evolution of human language. In the 1980s, psycholinguist
Myrna Gopnik identified a dominant gene that causes language impairment in the
KE family of Britain. This gene turned out to be a mutation of the FOXP2 gene. Humans have a unique allele of this gene, which has otherwise been closely conserved through most of mammalian evolutionary history. This unique allele appears to have first arisen between 100 and 200 thousand years ago, and it is now all but universal in humans. However, the once-popular idea that FOXP2 is a 'grammar gene' or that it triggered the emergence of language in
Homo sapiens is now widely discredited. Currently, several competing theories about the evolutionary origin of language coexist, none of them having achieved a general consensus. Researchers of language acquisition in primates and humans, such as
Michael Tomasello and
Talmy Givón, argue that the innatist framework has understated the role of imitation in learning and that it is not at all necessary to posit the existence of an innate grammar module to explain human language acquisition. Tomasello argues that studies of how children and primates actually acquire communicative skills suggest that humans learn complex behavior through experience, so that instead of a module specifically dedicated to language acquisition, language is acquired by the same cognitive mechanisms used to acquire all other kinds of socially transmitted behavior. On the issue of whether language is best seen as having evolved as an adaptation or as a spandrel, evolutionary biologist
W. Tecumseh Fitch, following
Stephen J. Gould, argues that it is unwarranted to assume that every aspect of language is an adaptation, or that language as a whole is an adaptation. He criticizes some strands of evolutionary psychology for suggesting a pan-adaptationist view of evolution, and dismisses Pinker and Bloom's question of whether "Language has evolved as an adaptation" as being misleading. He argues instead that from a biological viewpoint, the evolutionary origins of language are best conceptualized as being the probable result of a convergence of many separate adaptations into a complex system. A similar argument is made by
Terrence Deacon who in
The Symbolic Species argues that the different features of language have co-evolved with the evolution of the mind and that the ability to use symbolic communication is integrated in all other cognitive processes. If the theory that language could have evolved as a single adaptation is accepted, the question becomes which of its many functions has been the basis of adaptation. Several evolutionary hypotheses have been posited: that language evolved for social grooming, to signal mating potential, or to form social contracts. Evolutionary psychologists recognize that these theories are all speculative and that much more evidence is required to understand how language might have been selectively adapted.
Mating Given that sexual reproduction is the means by which genes are propagated into future generations, sexual selection plays a large role in human evolution. Human
mating, then, is of interest to evolutionary psychologists who aim to investigate evolved mechanisms for attracting and securing mates. Several lines of research have stemmed from this interest, such as studies of mate selection, mate poaching, mate retention,
mating preferences, and
conflict between the sexes. In 1972,
Robert Trivers published an influential paper on sex differences, which is now referred to as
parental investment theory. The size differences of
gametes (
anisogamy) are the fundamental, defining difference between males (small gametes – sperm) and females (large gametes – ova). Trivers noted that anisogamy typically results in different levels of parental investment between the sexes, with females initially investing more. Trivers proposed that this difference in parental investment leads to the
sexual selection of different
reproductive strategies between the sexes and to
sexual conflict. For example, he suggested that the sex that invests less in offspring will generally compete for access to the higher-investing sex to increase their
inclusive fitness. Trivers posited that differential parental investment led to the evolution of sexual dimorphisms in
mate choice, intra- and inter- sexual reproductive competition, and
courtship displays. In mammals, including humans, females make a much larger parental investment than males (i.e.,
gestation followed by childbirth and
lactation). Parental investment theory is a branch of
life history theory.
Buss and
Schmitt's 1993
sexual strategies theory proposed that, due to differential parental investment, humans have evolved sexually dimorphic adaptations related to Their strategic interference theory suggested that conflict between the sexes occurs when the preferred reproductive strategies of one sex interfere with those of the other sex, resulting in the activation of emotional responses such as anger or jealousy Women are generally more selective when choosing mates, especially under long-term mating conditions. However, under some circumstances, engaging in multiple sexual relationships can provide benefits to women as well, such as fertility insurance, trading up to better genes, reducing the risk of inbreeding, and insurance protection of her offspring. Due to male paternity uncertainty, sex differences have been found in the domains of
sexual jealousy. Females generally react more adversely to emotional infidelity, and males will react more to sexual infidelity. This pattern is predicted because mating costs differ between the sexes. Women, on average, should prefer a mate who can offer resources (e.g., financial, commitment); thus, a woman risks losing such resources when a mate commits emotional infidelity. Men, on the other hand, are never certain of the genetic paternity of their children because they do not bear the offspring themselves. This suggests that for men, sexual infidelity would generally be more aversive than emotional infidelity because investing resources in another man's offspring does not lead to the propagation of their own genes. Another interesting line of research examines women's mate preferences across the
ovulatory cycle. The theoretical underpinning of this research is that ancestral women would have evolved mechanisms to select mates with certain traits depending on their hormonal status. Known as the
ovulatory shift hypothesis, the theory posits that, during the ovulatory phase of a woman's cycle (approximately days 10–15 of a woman's cycle), a woman who mated with a male with high genetic quality would have been more likely, on average, to produce and bear a healthy offspring than a woman who mated with a male with low genetic quality. These putative preferences are expected to be especially apparent in short-term mating domains because a potential male mate would offer only genes to a potential offspring. This hypothesis allows researchers to examine whether women select mates with characteristics indicative of high genetic quality during the high fertility phase of their ovulatory cycles. Indeed, studies have shown that women's preferences vary across the ovulatory cycle. In particular, Haselton and Miller (2006) showed that highly fertile women prefer creative but poor men as short-term mates. Creativity may be a proxy for good genes. Research by Steven Gangestad in 2004 indicates that highly fertile women prefer men who display social presence and intrasexual competition; these traits may act as cues that help women predict which men may have, or be able to acquire, resources.
Parenting Reproduction inherently involves a cost for women, and men may also bear this cost. Individuals have limited time and resources to dedicate to their children, and this commitment can harm their own future health, survival, and reproductive potential. Parental investment is any parental expenditure (time, energy, etc.) that benefits one
offspring at a cost to parents' ability to invest in other components of fitness. Components of fitness (Beatty 1992Components of fitness (Beatty 1992) include the well-being of existing offspring, parents' future
reproduction, and inclusive fitness through aid to kin (
Hamilton, 1964). Parental investment theory is a branch of life history theory. The benefits of parental investment to the offspring are large and are associated with the effects on condition, growth, survival, and ultimately, on the reproductive success of the offspring. However, these benefits can come at the cost of the parent's future reproductive ability, e.g., increased risk of injury when defending offspring against predators, the loss of mating opportunities whilst rearing offspring, and an increase in the time to the next reproduction. Overall, parents are
selected to maximize the difference between the benefits and the costs, and parental care will likely evolve when the benefits exceed the costs. The
Cinderella effect is an alleged high incidence of stepchildren being physically, emotionally, or sexually abused, neglected, murdered, or otherwise mistreated at the hands of their stepparents at significantly higher rates than their genetic counterparts. It takes its name from the fairy tale character Cinderella, who in the story was cruelly mistreated by her stepmother and stepsisters. Martin Daly and Margo Wilson noted in their 1999 book:{{blockquote|text=''Evolutionary thinking led to the discovery of the most important risk factor for child homicide – the presence of a stepparent. Parental efforts and investments are valuable resources, and selection favors those parental psyches that allocate effort effectively to promote fitness. The adaptive problems that challenge parental decision-making include accurately identifying one's offspring, allocating resources among them with sensitivity to their needs and abilities, and converting parental investment into fitness increments.... Stepchildren were seldom or never so valuable to one's expected fitness as one's own offspring would be, and those parental psyches that were easily parasitized by just any appealing youngster must always have incurred a selective disadvantage.'' However, they note that not all stepparents will "want" to abuse their partner's children, or that genetic parenthood is any insurance against abuse. They see step-parental care as primarily "mating effort" towards the genetic parent.
Family and kin Inclusive fitness is the sum of an organism's classical fitness (how many of its own offspring it produces and supports) and the number of equivalents of its own offspring it can add to the population by supporting others. The first component is called classical fitness by Hamilton (1964). From the gene's point of view, evolutionary success ultimately depends on leaving behind the maximum number of copies of itself in the population. Until 1964, it was generally believed that genes only achieved this by causing the individual to leave the maximum number of viable offspring. However, in 1964, W. D. Hamilton proved mathematically that, because close relatives of an organism share some identical genes, a gene can also increase its evolutionary success by promoting the reproduction and survival of these related or otherwise similar individuals. Hamilton concluded that this leads natural selection to favor organisms that would behave in ways that maximize their inclusive fitness. It is also true that natural selection favors behavior that maximizes personal fitness. Hamilton's rule describes mathematically whether or not a gene for altruistic behavior will spread in a population: : where • is the reproductive cost to the altruist, • is the reproductive benefit to the recipient of the altruistic behavior, and • is the probability, above the population average, of the individuals sharing an altruistic gene – commonly viewed as "degree of relatedness". The concept explains how natural selection can perpetuate altruism. If there is an "altruism gene" (or complex of genes) that influences an organism's behavior to be helpful and protective of relatives and their offspring, this behavior also increases the proportion of the altruism gene in the population, because relatives are likely to share genes with the altruist due to
common descent. Altruists may also recognize altruistic behavior in unrelated individuals and be inclined to support them. As Dawkins points out in
The Selfish Gene (Chapter 6) and
The Extended Phenotype, this must be distinguished from the
green-beard effect. Although it is generally true that humans tend to be more altruistic toward their kin than toward non-kin, the relevant proximate mechanisms that mediate this cooperation have been debated (see
kin recognition), with some arguing that kin status is determined primarily via social and cultural factors (such as co-residence, maternal association of sibs, etc.), while others have argued that kin recognition can also be mediated by biological factors such as facial resemblance and immunogenetic similarity of the major histocompatibility complex (MHC). The interaction between these social and biological kin-recognition factors was discussed in the 2007
Nature (journal) article -
The architecture of human kin detection. Whatever the proximate mechanisms of kin recognition, there is substantial evidence that humans are generally more altruistic towards close genetic kin compared to genetic non-kin.
Interactions with non-kin / reciprocity Although interactions with non-kin are generally less altruistic compared to those with kin, cooperation can be maintained with non-kin via mutually beneficial reciprocity as was proposed by Robert Trivers If there are repeated encounters between the same two players in an evolutionary game in which each of them can choose either to "cooperate" or "defect", then a strategy of mutual cooperation may be favored even if it pays each player, in the short term, to defect when the other cooperates. Direct reciprocity can lead to the evolution of cooperation only if the probability, w, of another encounter between the same two individuals exceeds the cost-to-benefit ratio of the altruistic act: : Reciprocity can also be indirect if information about previous interactions is shared. Reputation enables the evolution of cooperation by indirect reciprocity. Natural selection favors strategies that base the decision to help on the recipient's reputation: studies show that people who are more helpful are more likely to receive help. The calculations of indirect reciprocity are complicated, and only a tiny fraction of this universe has been uncovered, but again, a simple rule has emerged. Indirect reciprocity can only promote cooperation if the probability, q, of knowing someone's reputation exceeds the cost-to-benefit ratio of the altruistic act: : One important problem with this explanation is that individuals may be able to evolve the capacity to obscure their reputations, reducing the probability, q, that it will be known. Trivers argues that friendship and various social emotions evolved in order to manage reciprocity. Liking and disliking, he says, evolved to help present-day humans' ancestors form coalitions with others who reciprocated and to exclude those who did not reciprocate. Moral indignation may have evolved to prevent one's altruism from being exploited by cheaters, and gratitude may have motivated present-day humans' ancestors to reciprocate appropriately after benefiting from others' altruism. Likewise, present-day humans feel guilty when they fail to reciprocate. These social motivations match what evolutionary psychologists expect to see in adaptations that evolved to maximize the benefits and minimize the drawbacks of reciprocity. According to evolutionary psychologists, humans possess psychological adaptations that developed to help us spot cheaters, also known as non-reciprocators. In 1993, Robert Frank and his associates found that participants in a prisoner's dilemma scenario were often able to predict whether their partners would "cheat", based on a half-hour of unstructured social interaction. In a 1996 experiment, for example,
Linda Mealey and her colleagues found that people were better at remembering faces when those faces were associated with stories about those individuals cheating (such as embezzling money from a church).
Strong reciprocity (or "tribal reciprocity") Humans may have an evolved set of psychological adaptations that predispose them to be more cooperative than otherwise would be expected with members of their tribal
in-group, and nastier to members of tribal
out-groups. These adaptations may have been a consequence of tribal warfare. Humans may also have predispositions for "
altruistic punishment" – to punish in-group members who violate in-group rules, even when this altruistic behavior cannot be justified in terms of helping those you are related to (
kin selection), cooperating with those who you will interact with again (
direct reciprocity), or cooperating to better your reputation with others (
indirect reciprocity). ==Evolutionary psychology and culture==