A psychological adaptation is a functional, cognitive or behavioral trait that benefits an organism in its environment. Psychological adaptations fall under the scope of evolved psychological mechanisms (EPMs), however, EPMs refer to a less restricted set. Psychological adaptations include only the functional traits that increase the fitness of an organism, while EPMs refer to any psychological mechanism that developed through the processes of evolution. These additional EPMs are the by-product traits of a species’ evolutionary development (see spandrels), as well as the vestigial traits that no longer benefit the species’ fitness. It can be difficult to tell whether a trait is vestigial or not, so some literature is more lenient and refers to vestigial traits as adaptations, even though they may no longer have adaptive functionality. For example, xenophobic attitudes and behaviors, some have claimed, appear to have certain EPM influences relating to disease aversion, however, in many environments these behaviors will have a detrimental effect on a person's fitness. The principles of psychological adaptation rely on Darwin's theory of evolution and are important to the fields of evolutionary psychology, biology, and cognitive science.
Darwinian theory
Charles Darwin proposed his theory of evolution in On the Origin of Species (1859). His theory dictates that adaptations are traits that arise from the selective pressures a species faces in its environment. Adaptations must benefit either an organism's chance of survival or reproduction to be considered adaptive, and are then passed down to the next generation through this process of natural selection. Psychological adaptations are those adaptive traits that we consider cognitive or behavioral. These can include conscious social strategies, subconscious emotional responses (guilt, fear, etc.), or the most innate instincts. Evolutionary psychologists consider a number of factors in what determines a psychological adaptation, such as functionality, complexity, efficiency, and universality. The Adapted Mind is considered a foundational text on evolutionary psychology, further integrating Darwinian theory into modern psychology.
Evolved adaptation vs learned behaviour An area of disagreement arises between evolutionary psychologists, cognitive scientists and behaviourists on where to draw the line on what is considered a psychological adaptation, and what is considered a learned behaviour.Buss, D.M. (2004) Evolutionary psychology: The new science of the mind. Evolutionary Psychology 3rd Ed. Boston. Where behaviourism explains certain behaviours as conditioned responses, cognitivism may push that these behaviours arise from a psychological adaptation that institutes a preference for that behaviour. Evolutionary psychology proposes that the human psychology consists primarily of psychological adaptations, which is opposed by the tabula rasa or blank slate model of human psychology. Early behaviourists, like B.F. Skinner, tended to the blank slate model and argued that innate behaviors and instincts were few, some behaviourists suggesting that the only innate behavior was the ability to learn. On the other hand, Steven Pinker presents the cognitivist perspective in his book, The Blank Slate, in which he challenges the tabula rasa models and argues that human behaviour is shaped by psychological adaptations.Pinker, Steven. (2002) The blank slate: The modern denial of human nature. Allen Lane, London. Print
This difference in theory can be seen in research on modern human sexual preferences, with behaviourists arguing that attraction has conditioning influences, such as from the media or cultural norms, while others arguing it is based on psychological adaptations. However, sexual preferences are a difficult subject to test due to the amount of variance and flexibility exhibited in human mate choice.Miller, G.F. (1997) Mate choice: From sexual cues to cognitive adaptations. Ciba Foundation Symposium, 208:71-87. A hybrid resolution to psychological adaptations and learned behaviours refers to an adaptation as the species’ capacity for a certain behavior, while each individual organism still needs to be conditioned to exhibit that behaviour. This approach can explain language acquisition in relation to linguist and cognitive scientist Noam Chomsky's model of human language.Lenneberg, E. H., Chomsky, N., & Marx, O. (1967). Biological foundations of language (Vol. 68). New York: Wiley. http://tocs.ulb.tu-darmstadt.de/123135893.pdf His model supports that the capacity for language is a psychological adaptation (involving both the language necessary brain structures and disposition for language acquisition), however, children lack any particular instantiation of language at birth, and must instead learn one in their environment.
Sexual selection The mating strategies of both sexes can be simplified into different psychological adaptations. There is extensive evidence that incest avoidance, which is the tendency to avoid sexual intercourse with close relatives is an evolved behavioural adaptation. Incest avoidance can be seen cross-culturally in humans, and is evident in wild animals. Evolutionary psychologists argue that incest avoidance adapted due to the greater chance of producing children with severe disabilities when mating with relatives, and because genetic variability offers an increase in fitness regarding offspring survival. Sexual jealousy is another behavior observed in human and non-human animals that appears to be instinctual. Heuristic problem solving and consistent preference for behavioral patterns are considered by some evolutionary psychologists to be psychological adaptations.Buss, D.M., Kruger, D., Kurzban, R. et al. (2009) Evolutionary theory and psychology. Psychological Science Agenda, Science Briefs. http://www.apa.org/science/about/psa/2009/05/sci-brief.aspx#Machery For example, the tendency for females to change their sexual strategies when faced with developmental pressures such as an absent father may be the result of a psychological adaptation.
Psychological adaptation in males
Human males may have developed psychological adaptations, which could influence reported patterns in intersexual (appearing attractive to the opposite sex) and intrasexual (restricting competitors of the same-sex) mating "strategies" in ways that increase their reproductive success. Examples of possible adaptations include behaviors that advertise mate quality, retention tactics, and short/long-term mating preferences.
Humour It has been researched that humour is sexually selected and acts as a fitness indicator.Greengross, G. (2014). Male production of humour produced by sexually selected psychological adaptations. In Shackelford, V. A & Shackelford, T. K. (2014). Evolutionary perspectives on human sexual psychology and behaviour(173-196). New York:Springer. According to this research it was theorized that the production of humour increases "mate value" in men, and some women seek men with a good sense of humour. In turn, some men are believed to have developed an adaptation in which they endeavour to produce humour with the aim to attract female mates.
Mate preferences Though significant cultural variability exists in both male and female mate preferences, evolutionary psychologists predict that preferences in males could have adaptive explanations, as indicated by correlative studies on female attractiveness and cues of reproductive value, such as a waist–hip ratio. Women with a waist-to-hip ratio of 0.7 are, in some samples, considered more attractive on average to males than those with ratios above or below.
Mate retention Males could have developed behaviours that aid mate retention, also known as mate guarding, in order to increase reproductive success in long-term relationships. Observations of possible male mate retention behaviors include intrasexual and intersexual strategies, such as derogating rival males.Starratt, V. G., & Alesia, M. N. (2014). Male adaptations to retain a mate. In Shackelford, V. A., & Shackelford, T. K. (2014). Evolutionary perspectives on human sexual psychology and behaviour 197-205. New York:Springer. When considering the influence of non-evolutionary (e.g., cultural/economic) factors, males in some environments have been observed restricting mate interactions with other men and/or using coercion/violence to control mates. Intrasexual strategies that have also been observed and are potentially adaptive include public displays of mate possession or intimidation tactics that discourage rival communication with said mate.
Long-term mating In regards to parental investment, some hypotheses posit that, when compared to short-term mating, males display risk-averse mate-choice behaviors in long-term (committed) relationships, as investing in offspring is energetically and emotionally costly and involves inherent risks considering the issue of "paternity uncertainty".Trivers, R. L. (1972). "Parental investment and sexual selection ". In Campbell, B, (Ed.), Sexual selection and the descent of man, 1871-1971, 136–179. London: Heinemann. Therefore, as an adaptation, males investment patterns and any potential genes underlying them could be partially understood by trade-offs in ancestral conditions.
Short-term mating Male short-term mating is reportedly more common than females in cross-cultural analyses, with both historical (non-genetic) and evolutionary explanations providing insight into the origin(s) of this difference. Evolutionary explanations utilize frameworks based on minimum female parental investment (nine months of gestation), in which conception inherently poses a higher investment potential without the use of birth control methods. Additionally, preferences for sexual variety and novelty are typically higher in males, a finding that some scholars use as support for adaptive explanations of these behavioral patterns. Furthermore, males are consistently higher in risk-taking and motivation when provided opportunity for sexual experiences with lower levels of commitment and familiarity, as is illustrated in several studies that found male participants more likely than women to have sexual intercourse with someone having known them for only one hour, one day, one week, or one month.
Psychological adaptation in females
Human female sexually-differentiated mating tendencies provide possible evidence of adaptations that, ancestrally, may have increased fitness and reproductive success.Williams, G.C. (1996). Adaptation and natural selection. Princeton, NJ: Princeton University Press. For example, mate choice, threat aversion tactics and pregnancy sickness are all hypothesized to be female-specific psychological adaptations, identified through empirical research, and are predicted to have increased genetic contributions through survival and reproduction.Alcock, J. (1993). Animal behaviour: An evolutionary approach. Sunderland, MA: Sinauer.
Mate-choice as an adaptation