Evolutionary psychology is a theoretical approach in psychology that examines cognition and behavior from a modern evolutionary perspective. It seeks to identify human psychological adaptations with regard to the ancestral problems they evolved to solve. In this framework, psychological traits and mechanisms are either functional products of natural and sexual selection or non-adaptive by-products of other adaptive traits. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and the liver, is common in evolutionary biology. Evolutionary psychologists apply the same line of thinking in psychology, arguing that just as the heart evolved to pump blood, the liver evolved to detoxify poisons, and the kidneys evolved to filter turbid fluids, there is modularity of mind, in that different psychological mechanisms evolved to solve distinct adaptive problems. The evolutionary psychologists argue that much of human behavior is the output of psychological adaptations that evolved to solve recurrent problems in human ancestral environments. Some evolutionary psychologists argue that evolutionary theory can provide a foundational, metatheoretical framework that integrates the entire field of psychology, much as evolutionary biology has done for biology. Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations, including the abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. Findings have been made regarding human social behaviour related to infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price, and parental investment. The theories and findings of evolutionary psychology have applications in many fields, including economics, environment, health, law, management, psychiatry, politics, and literature. Criticism of evolutionary psychology involves questions of testability, cognitive and evolutionary assumptions (such as modular functioning of the brain, and large uncertainty about the ancestral environment), importance of non-genetic and non-adaptive explanations, and political and ethical implications of interpretations of research results.
Scope
Principles The central assumption of evolutionary psychology is that the human brain is composed of many specialized mechanisms that were shaped by natural selection over a vast period of time to solve the recurrent information-processing problems faced by our ancestors. These problems involve food choices, social hierarchies, the distribution of resources to offspring, and selecting mates. Proponents suggest that it seeks to integrate psychology into the other natural sciences, rooting it in the organizing theory of biology (evolutionary theory), and thus understanding psychology as a branch of biology. Anthropologist John Tooby and psychologist Leda Cosmides wrote:Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed, fragmentary, and mutually contradictory human disciplines a single, logically integrated research framework for the psychological, social, and behavioral sciences – a framework that not only incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of the revisions in existing belief and research practice that such a synthesis requires. Just as human physiology and evolutionary physiology have worked to identify physical adaptations of the body that represent "human physiological nature," the purpose of evolutionary psychology is to identify evolved emotional and cognitive adaptations that represent "human psychological nature." According to Steven Pinker, it is "not a single theory but a large set of hypotheses" and a term that "has also come to refer to a particular way of applying evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity." Evolutionary psychology adopts an understanding of the mind grounded in the computational theory of mind. It describes mental processes as computational operations, so that, for example, a fear response is described as arising from a neurological computation that takes perceptual data, e.g., a visual image of a spider, and outputs the appropriate reaction, e.g., fear of possibly dangerous animals. Under this view, any domain-general learning is impossible because of the combinatorial explosion. Evolutionary psychology specifies the domain as the problems of survival and reproduction. While philosophers have generally considered the human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe evolved psychological mechanisms as narrowly focused on specific issues, such as catching cheaters or choosing mates. The discipline sees the human brain as having evolved specialized functions, called cognitive modules, or psychological adaptations which are shaped by natural selection. Examples include language-acquisition modules, incest-avoidance mechanisms, cheater-detection mechanisms, intelligence and sex-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent-detection mechanisms, and others. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, are proposed to deal with evolutionary novelty. Evolutionary psychology has roots in cognitive psychology and evolutionary biology but also draws on behavioral ecology, artificial intelligence, genetics, ethology, anthropology, archaeology, biology, ecopsychology and zoology. It is closely linked to sociobiology, but there are key differences between them including the emphasis on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness, the importance of mismatch theory, and psychology rather than behavior. Nikolaas Tinbergen's four categories of questions can help clarify the distinctions among several complementary types of explanations. Evolutionary psychology focuses primarily on the "why?" questions, while traditional psychology focuses on the "how?" questions.
Premises Evolutionary psychology is founded on several core premises.
The brain is an information-processing device, and it produces behavior in response to external and internal inputs. The brain's adaptive mechanisms were shaped by natural and sexual selection. Different neural mechanisms are specialized for solving problems in humanity's evolutionary past. The brain has evolved specialized neural mechanisms that were designed for solving problems that recurred over deep evolutionary time, giving modern humans stone-age minds. Most contents and processes of the brain are unconscious, and most mental problems that seem easy to solve are actually extremely difficult problems that are solved unconsciously by complicated neural mechanisms. Human psychology comprises many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.
History
Evolutionary psychology has its historical roots in Charles Darwin's theory of natural selection. In his book On the Origin of Species, Darwin predicted that psychology would develop an evolutionary basis:In the distant future I see open fields for far more important research. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Upon completing On the Origin of Species in 1859, Darwin shifted his focus to creating an evolution-based psychology, having viewed the development of an evolutionary explanation for higher human faculties as his most crucial undertaking since conceiving his theory of evolution in the late 1830s. He devoted more than a decade to study of the evolutionary origins of key aspects of human behaviour, in particular: the human intellect; rationality; human sexual behaviour; emotional expressions; moral behaviour; language; culture; and conscience—several of which Darwin argued had originated due to the unusual ways natural selection operates in social animals, that is, by different kinds of group selection, including kin selection and reciprocal altruism. Initially conceived as groundwork for one book, Darwin's psychological project became so large and fruitful that he split it into two parts, the first being published as The Descent of Man, and Selection in Relation to Sex in 1871 and the second as The Expression of the Emotions in Man and Animals in 1872. Darwin also published pathbreaking evolutionary monographs on insect and invertebrate behaviour, and—believing that infant behaviour gives us privileged access to humans' evolutionary endowment—a seminal case-study of his baby son William's behaviour, containing many observations confirmed by recent research, including those on: infant-adult communication and meta-communication; infant emotional expressions; early reasoning; the experimental study of infant jealousy; and the origins of self-knowledge. Darwin's evolutionary psychological publications inspired many of the founders of modern psychology, including: Sigmund Freud and his theories of psychoanalysis, particularly as relating to the Oedipus complex and group psychology; both the physiological and folk psychologies of Wilhelm Wundt; William James's functionalist approach to psychology; the genetic psychology of James Mark Baldwin and thus, indirectly, Jean Piaget; the social behaviourism or symbolic interactionism of George Herbert Mead which set out from Mead's appropriation of Darwin's treatment of gesture and attitude in his book on Expression; and the study of evolved 'instinctive' behaviour in animals—a major topic in On the Origin of Species—known today as ethology and pioneered by Konrad Lorenz, Karl von Frisch and Niko Tinbergen. More recently, Darwin's research on his baby son inspired Colwyn Trevarthen's observational approach to infancy and his theory of innate intersubjectivity. Overall, Darwin's theories of evolution, adaptation, and natural selection have provided and continue to provide many insights into why minds and brains function the way they do. 20th century evolutionary psychologies mostly bypass Darwin's extensive evolutionary treatment of human psychology, drawing instead from: the biological sciences of their day—especially 20th century evolutionary theory as it is imagined to relate to ancient human environments; the study of paleoanthropology; ethology; and various human sciences, most obviously cognitive psychology. For example, writing from a gene-centred perspective on evolution, W.D. Hamilton's (1964) papers on inclusive fitness and Robert Trivers's (1972) theories on reciprocity and parental investment helped to re-establish evolutionary thinking in psychology and the other social sciences, though without reference to the place of parental investment, reciprocal altruism and kin selection in Darwin's psychology. Likewise, in 1975, Edward O. Wilson combined evolutionary theory with studies of animal and social behavior, principally referencing the works of Lorenz and Tinbergen, in his book Sociobiology: The New Synthesis. In the 1970s, two major branches of ethology developed. Firstly, the study of animal social behavior (including humans) generated sociobiology, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic study of the biological basis of all social behavior." and in 1978 as "the extension of population biology and evolutionary theory to social organization." Secondly, there was behavioral ecology, which placed less emphasis on social behavior; it focused on the ecological and evolutionary basis of animal and human behavior. In the 1970s and 1980s, university departments began to include the term evolutionary biology in their titles. The modern era of evolutionary psychology was ushered in, in particular, by Donald Symons' 1979 book The Evolution of Human Sexuality and Leda Cosmides and John Tooby's 1992 book The Adapted Mind. David Buller observed that the term "evolutionary psychology" is sometimes seen as denoting research based on the specific methodological and theoretical commitments of certain researchers from the Santa Barbara school (University of California), thus some evolutionary psychologists prefer to term their work "human ecology", "human behavioural ecology" or "evolutionary anthropology" instead.
In psychology, there are the primary streams of developmental, social, and cognitive psychology. Establishing some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral genetics and its variants, notably studies at the molecular level that examine the relationship between genes, neurotransmitters, and behavior. Dual inheritance theory (DIT), developed in the late 1970s and early 1980s, has a slightly different perspective by trying to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution. DIT is seen by some as a "middle-ground" between views that emphasize human universals versus those that emphasize cultural variation.
Theoretical foundations
The theories on which evolutionary psychology is based originated with Charles Darwin's work, including his speculations about the evolutionary origins of social instincts in humans. Modern evolutionary psychology, however, is possible only because of advances in evolutionary theory in the 20th century. Evolutionary psychologists say that natural selection has provided humans with many psychological adaptations, much the same way it has generated humans' anatomical and physiological adaptations. As with adaptations in general, psychological adaptations are said to be specialized for the environment in which an organism evolved, the environment of evolutionary adaptedness. Sexual selection provides organisms with adaptations related to mating. For male mammals, which have a relatively high maximal potential reproduction rate, sexual selection leads to adaptations that help them compete for females. For female mammals, with a relatively low maximal potential reproduction rate, sexual selection leads to choosiness, which helps females select higher-quality mates. Charles Darwin described both natural selection and sexual selection, and he relied on group selection to explain the evolution of altruistic (self-sacrificing) behavior. But group selection was argued to be a weak explanation by those who adopted the 20th century's individualistic gene-centred view of evolution, because it was thought that in any loosely-bonded group which lacked strong in-group dynamics (of the kind assumed by Darwin), less altruistic individuals will be more likely to survive, and the group will become less self-sacrificing as a whole. In 1964, the evolutionary biologist William D. Hamilton proposed inclusive fitness theory, emphasizing a gene-centered view of evolution. Hamilton noted that genes can increase the replication of copies of themselves into the next generation by influencing the organism's social traits in such a way that (statistically) results in helping the survival and reproduction of other copies of the same genes (most simply, identical copies in the organism's close relatives). According to Hamilton's rule, self-sacrificing behaviors (and the genes influencing them) can evolve if they typically help the organism's close relatives so much that it more than compensates for the individual animal's sacrifice. Inclusive fitness theory resolved the issue of how altruism can evolve. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory, tit-for-tat reciprocity, and generalized reciprocity. These theories help to explain the development of altruistic behavior, and account for hostility toward cheaters (individuals that take advantage of others' altruism). Several mid-level evolutionary theories inform evolutionary psychology. The r/K selection theory proposes that some species prosper by having many offspring, while others follow the strategy of having fewer offspring but investing much more in each one. Humans follow the second strategy. Parental investment theory explains how parents invest more or less in individual offspring based on how successful those offspring are likely to be, and thus how much they might improve the parents' inclusive fitness. According to the Trivers–Willard hypothesis, parents in good conditions tend to invest more in sons (who are best able to take advantage of good conditions), while parents in poor conditions tend to invest more in daughters (who are best able to have successful offspring even in poor conditions). According to life history theory, animals evolve life histories to match their environments, determining details such as age at first reproduction and number of offspring. Dual inheritance theory posits that genes and human culture have interacted, with genes affecting the development of culture and culture, in turn, affecting human evolution on a genetic level, in a similar way to the Baldwin effect.
Evolved psychological mechanisms
Evolutionary psychology posits that psychological traits, like biological organs, have a genetic foundation and have developed through natural selection. Therefore, cognition, having a genetic foundation, is functionally structured and has evolved through natural selection. Similar to other organs and tissues, this functional structure ought to be common to all individuals of a species, tackling essential challenges for survival and reproduction. Evolutionary psychologists seek to understand psychological mechanisms by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others, and follow leaders. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. For instance, a mother may wish to wean her offspring from breastfeeding earlier than her infant does, freeing her to invest in additional offspring. Evolutionary psychology also recognizes the roles of kin selection and reciprocity in the evolution of prosocial traits such as altruism. Like chimpanzees and bonobos, humans have subtle and flexible social instincts, allowing them to form extended families, lifelong friendships, and political alliances. In studies testing theoretical predictions, evolutionary psychologists have made modest findings on topics such as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price, and parental investment. Another example would be the evolved mechanism in depression. Clinical depression is maladaptive and should have evolutionary approaches so it can become adaptive. Over the centuries, animals and humans have endured hard times to survive, leading to the evolution of our fight-or-flight sense. For instance, mammals have separation anxiety from their guardians, which causes distress and sends signals to their hypothalamic pituitary adrenal axis, and emotional/behavioral changes. Going through these types of circumstances helps mammals cope with separation anxiety.
Historical topics Proponents of evolutionary psychology in the 1990s explored historical events, but the response from historical experts was highly negative, and there has been little effort to continue that line of research. Historian Lynn Hunt says that the historians complained that the researchers:have read the wrong studies, misinterpreted the results of experiments, or worse yet, turned to neuroscience looking for a universalizing, anti-representational, and anti-intentional ontology to bolster their claims. Hunt states that "the few attempts to build up a subfield of psychohistory collapsed under the weight of its presuppositions." She concludes that, as of 2014, the "'iron curtain' between historians and psychology...remains standing."
Products of evolution: adaptations, exaptations, byproducts, and random variation Not all traits of organisms are evolutionary adaptations. As noted in the table below, traits may also be exaptations, byproducts of adaptations (sometimes called "spandrels"), or random variation between individuals. Psychological adaptations are hypothesized to be innate or relatively easy to learn and to manifest in cultures worldwide. For example, the toddler's ability to learn a language with virtually no training is likely to be a psychological adaptation. On the other hand, ancestral humans did not read or write; thus, today, learning to read and write requires extensive training, and presumably involves the repurposing of cognitive capacities that evolved under selection pressures unrelated to written language. However, variations in manifest behavior can result from universal mechanisms interacting with different local environments. For example, Caucasians who move from a northern climate to the equator will have darker skin. The mechanisms regulating their pigmentation do not change; rather, the input to those mechanisms changes, resulting in different outputs.
One of the tasks of evolutionary psychology is to identify which psychological traits are likely to be adaptations, byproducts, or random variation. George C. Williams suggested that an"adaptation is a special and onerous concept that should only be used where it is really necessary." As noted by Williams and others, adaptations can be identified by their improbable complexity, species universality, and adaptive functionality.
Obligate and facultative adaptations A question that may be asked about an adaptation is whether it is generally obligate (relatively robust in the face of typical environmental variation) or facultative (sensitive to typical environmental variation). The sweet taste of sugar and the pain of hitting one's knee against concrete are the result of fairly obligate psychological adaptations; typical environmental variability during development does not much affect their operation. By contrast, facultative adaptations are somewhat like "if-then" statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, our propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers can be trusted to provide reliable assistance and attention. The adaptation for skin to tan is conditional on exposure to sunlight; this is an example of another facultative adaptation. When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence its expression.
Cultural universals
Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. Cultural universals include behaviors related to language, cognition, social roles, gender roles, and technology. Evolved psychological adaptations (such as the ability to learn a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned). Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females. It has been found that both male and female personality traits vary across a wide spectrum. Males had a higher rate of traits relating to dominance, tension, and directness. Females had higher rates of organizational behavior and more emotionally-oriented characteristics. Evolutionary psychologists contrast their approach to what they term the "standard social science model," according to which the mind is a general-purpose cognition device shaped almost entirely by culture.
Environment of evolutionary adaptedness
Evolutionary psychology argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the "environment of evolutionary adaptiveness." The idea of an environment of evolutionary adaptedness was first explored as a part of attachment theory by John Bowlby. This is the environment to which a particular evolved mechanism is adapted. More specifically, the environment of evolutionary adaptedness is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation. Humans, the genus Homo, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides with the start of the Pleistocene 2.6 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most human adaptations either evolved during the Pleistocene or were maintained by stabilizing selection during the Pleistocene. Evolutionary psychology, therefore, proposes that most of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments. In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships. The environment of evolutionary adaptation is significantly different from modern society. The ancestors of modern humans lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning.> Researchers look to existing hunter-gatherer societies for clues as to how hunter-gatherers lived in the environment of evolutionary adaptation. Unfortunately, the few surviving hunter-gatherer societies differ from each other, and they have been pushed out of the best land and into harsh environments, so it is not clear how closely they reflect ancestral culture. However, across the world, small-band hunter-gatherers offer a similar developmental system for the young. The characteristics of the niche are largely the same as for social mammals, who evolved over 30 million years ago: soothing perinatal experience, several years of on-demand breastfeeding, nearly constant affection or physical proximity, responsiveness to need (mitigating offspring distress), self-directed play, and, for humans, multiple responsive caregivers. Initial studies show the importance of these components in early life for positive child outcomes. Evolutionary psychologists sometimes look to chimpanzees, bonobos, and other great apes for insights into human ancestral behavior.
Mismatches
When an organism's traits are suited for its old environment, a change in surroundings can result in a mismatch. Our minds, evolved for Pleistocene environments, may possess traits incongruent with the modern world. For instance, it is noteworthy that more than 20,000 people in the US die from gun violence each year. However, spiders and snakes are responsible for very few fatalities. Even so, individuals acquire a fear of spiders and snakes as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits, or flowers. One possible reason is that spiders and snakes posed a danger to early humans during the Pleistocene, unlike guns, rabbits, and flowers. There is a mismatch between our evolved fear responses and the modern world. This mismatch also shows up in the phenomenon of the supernormal stimulus, a stimulus that elicits a response more strongly than the stimulus for which the response evolved. The term was coined by Niko Tinbergen to refer to non-human animal behavior, but psychologist Deirdre Barrett said that supernormal stimulation governs human behavior as powerfully as that of other animals. She explained junk food as an exaggerated stimulus for cravings for salt, sugar, and fat, and she says that television exaggerates social cues of laughter, smiling faces, and attention-grabbing action. Magazine centerfolds and double cheeseburgers pull instincts intended for an environment of evolutionary adaptedness where breast development was a sign of health, youth, and fertility in a prospective mate, and fat was a rare and vital nutrient. The psychologist Mark van Vugt recently argued that modern organizational leadership is a mismatch. His argument is that humans are not adapted to work in large, anonymous bureaucratic structures with formal hierarchies. The human mind still responds to personalized, charismatic leadership primarily in informal, egalitarian settings. Hence, the dissatisfaction and alienation that many employees experience. Salaries, bonuses, and other privileges exploit instincts for relative status, which attract men in particular to senior executive positions.
Research methods Evolutionary theory is heuristic in that it may generate hypotheses that might not be developed from other theoretical approaches. One of the main goals of adaptationist research is to identify which organismic traits are likely to be adaptations, and which are byproducts or random variations. As noted earlier, adaptations are expected to show evidence of complexity, functionality, and species universality, while byproducts or random variation will not. In addition, adaptations are expected to be presented as proximate mechanisms that interact with the environment in either a generally obligate or facultative fashion (see above). Evolutionary psychologists are also interested in identifying these proximate mechanisms (sometimes termed "mental mechanisms" or "psychological adaptations") and what type of information they take as input, how they process that information, and their outputs. Evolutionary developmental psychology, or "evo-devo," focuses on how adaptations may be activated at certain developmental times (e.g., losing baby teeth, adolescence, etc.) or how events during the development of an individual may alter life-history trajectories.
Evolutionary psychologists use several strategies to develop and test hypotheses about whether a psychological trait is likely to be an evolved adaptation. David Buss notes that these methods include: Cross-cultural Consistency. Characteristics that have been demonstrated to be cross-cultural human universals, such as smiling, crying, and facial expressions, are presumed to be evolved psychological adaptations. Several evolutionary psychologists have collected massive datasets from cultures around the world to assess cross-cultural universality. Function to Form (or "problem to solution"). The fact that males, but not females, risk potential misidentification of genetic offspring (referred to as "paternity uncertainty") led evolutionary psychologists to hypothesize that, compared to females, male jealousy would be more focused on sexual than on emotional infidelity. Form to Function (reverse-engineering – or "solution to problem"). Morning sickness and associated food aversions during pregnancy seemed to have the characteristics of an evolved adaptation (complexity and universality). Margie Profet hypothesized that the function was to avoid the ingestion of toxins during early pregnancy that could damage the fetus (but which are otherwise likely to be harmless to healthy non-pregnant women). Corresponding Neurological Modules. Evolutionary psychology and cognitive neuropsychology are mutually compatible – evolutionary psychology helps to identify psychological adaptations and their ultimate, evolutionary functions, while neuropsychology helps to identify the proximate manifestations of these adaptations. Current Evolutionary Adaptiveness. In addition to evolutionary models that suggest evolution occurs over long timescales, recent research has demonstrated that some evolutionary shifts can be fast and dramatic. Consequently, some evolutionary psychologists have focused on the impact of psychological traits in the current environment. Such research can inform estimates of trait prevalence over time. Such work has been informative in the study of evolutionary psychopathology.
Evolutionary psychologists also use various sources of data for testing, including experiments, archaeological records, data from hunter-gatherer societies, observational studies, neuroscience data, self-reports and surveys, public records, and human products. Recently, additional methods and tools have been introduced based on fictional scenarios, mathematical models, and multi-agent computer simulations.
Main areas of research 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