Editing Evolutionary psychology (section)

===Abnormal psychology===
{{Main|Evolutionary psychiatry}}
Adaptationist hypotheses regarding the etiology of psychological disorders are often based on analogies between physiological and psychological dysfunctions,<ref>{{cite book |last1=Nesse |first1=R |last2=Williams |first2=George C. |title=Why We Get Sick |year=1996 |publisher=Vintage |location=NY|author1-link=Randolph M. Nesse |author2-link=George C. Williams (biologist) }} (adaptationist perspective to both physiological and psychological dysfunctions)</ref> as noted in the table below. Prominent theorists and evolutionary psychiatrists include [[Michael T. McGuire]], [[Anthony Stevens (Jungian analyst)|Anthony Stevens]], and [[Randolph M. Nesse]]. They, and others, suggest that mental disorders are due to the interactive effects of both nature and nurture, and often have multiple contributing causes.<ref name=Gaulin-Steven-J-C-2003-pp.1-24/>

{| class="wikitable"
|-
|+ Possible causes of psychological 'abnormalities' from an adaptationist perspective <br />
<small>Summary based on information in these textbooks (all titled "Evolutionary Psychology"): Buss (2011),<ref name="ReferenceA" /> Gaulin & McBurney (2004),<ref name="Gaulin-2004" /> Workman & Reader (2008)<ref>Workman & Reader (2008), Evolutionary Psychology, 2nd Ed. Cambridge: Cambridge University Press,</ref> as well as Cosmides & Tooby (1999) ''Toward an evolutionary taxonomy of treatable conditions''<ref>{{cite journal |last1=Cosmides |first1=L. |last2=Tooby |first2=J. |year=1999 |title=Toward an evolutionary taxonomy of treatable conditions |journal=Journal of Abnormal Psychology |volume=108 |issue=3| pages=453–64 |doi=10.1037/0021-843X.108.3.453 |pmid=10466269 }}</ref></small>
|-
! Causal mechanism of failure or malfunction of adaptation !! Physiological Example !! Hypothesized Psychological Example
|-
| '''Functioning adaptation (adaptive defense)'''
| Fever / Vomiting <br><small>(functional responses to infection or ingestion of toxins)</small>
| Mild depression or anxiety <small>(functional responses to mild loss or stress</small><ref name=ncbi.nlm.nih.gov>{{cite journal | last1 = Andrews | first1 = P. W. | last2 = Thomson | first2 = J. A. | date = July 2009 | title = The bright side of being blue: Depression as an adaptation for analyzing complex problems | journal = Psychol. Rev. | volume = 116 | issue = 3| pages = 620–654 | doi = 10.1037/a0016242 | pmid = 19618990 | pmc = 2734449 }}</ref><small>/ reduction of social interactions to prevent infection by contagious pathogens)</small><ref>Raison, C.L, Miller, A. N. (2012). The evolutionary significance of depression in Pathogen Host Defense (PATHOS-D) Molecular Psychiatry 1–23. [http://www.nature.com/mp/journal/vaop/ncurrent/pdf/mp20122a.pdf PDF].</ref>
|-
|'''By-product of an adaptation(s)'''
| Intestinal gas <br><small>(byproduct of digestion of fiber)</small>
| [[Sexual fetishism|Sexual fetishes]] (?)<br><small>(possible byproduct of normal sexual arousal adaptations that have 'imprinted' on unusual objects or situations)</small>
|-
| '''Adaptations with multiple effects'''
| [[Sickle cell disease]] <small>(Gene that imparts malaria resistance, in homozygous form, causes sickle cell anemia)</small>
| [[Schizophrenia]] or [[bipolar disorder]] <small>(May be side-effects of adaptations for high levels of creativity, perhaps dependent on alternate developmental trajectories)</small>
|-
| '''Malfunctioning adaptation'''
| Allergies <br><small>(over-reactive immunological responses)</small>
| [[Autism]] <br><small>(possible malfunctioning of [[theory of mind]] module)</small>
|-
| '''[[Frequency-dependent selection|Frequency-dependent]] morphs'''
| The two sexes / Different blood and immune system types
| [[Personality disorders]] <br><small>(may represent alternative behavioral strategies possibly dependent on its prevalence in the population)</small>
|-
| '''Mismatch between ancestral & current environments'''
| [[Type 2 Diabetes]] <br><small>(May be related to the abundance of sugary foods in the modern world)</small>
| More frequent modern interaction with strangers (compared to family and close friends) may predispose greater incidence of depression & anxiety
|-
| '''Tails of [[normal distribution]] (bell curve)'''
| [[Dwarfism]] or [[gigantism]]
| Extremities of the distribution of cognitive and personality traits<br><small>(e.g., extremely introversion and extraversion, or [[intellectual giftedness]] and [[intellectual disability]])</small>
|}

Evolutionary psychologists have suggested that schizophrenia and bipolar disorder may reflect a side-effect of genes with fitness benefits, such as increased creativity.<ref name=Gaulin-11>Gaulin and McBurney 2003 pp. 239–56.</ref> (Some individuals with bipolar disorder are especially creative during their manic phases and the close relatives of people with schizophrenia have been found to be more likely to have creative professions.<ref name=Gaulin-11/>) A 1994 report by the American Psychiatry Association found that people with schizophrenia at roughly the same rate in Western and non-Western cultures, and in industrialized and pastoral societies, suggesting that schizophrenia is not a disease of civilization nor an arbitrary social invention.<ref name=Gaulin-11/> Sociopathy may represent an evolutionarily stable strategy, by which a small number of people who cheat on social contracts benefit in a society consisting mostly of non-sociopaths.<ref name=Gaulin-Steven-J-C-2003-pp.1-24/> Mild depression may be an adaptive response to withdraw from, and re-evaluate, situations that have led to disadvantageous outcomes (the "analytical rumination hypothesis")<ref name=ncbi.nlm.nih.gov/> (see [[Evolutionary approaches to depression]]).

Trofimova reviewed the most consistent psychological and behavioural sex differences in psychological abilities and disabilities and linked them to the Geodakyan's evolutionary theory of sex (ETS).<ref name=Trofimova> {{cite journal|last1=Trofimova |first1=I.|year=2015| title= Do psychological sex differences reflect evolutionary bi-sexual partitioning? |journal =American Journal of Psychology|volume=128 |issue=4 |pages=485–514|doi= 10.5406/amerjpsyc.128.4.0485| pmid=26721176}}</ref> She pointed out that a pattern of consistent sex differences in physical, verbal and social dis/abilities corresponds to the idea of the ETS considering sex dimorphism as a functional specialization of a species. Sex differentiation, according to the ETS, creates two partitions within a species, (1) conservational (females), and (2) variational (males). In females, superiority in verbal abilities, higher rule obedience, socialisation, empathy and agreeableness can be presented as a reflection of the systemic conservation function of the female sex. Male superiority is mostly noted in exploratory abilities - in risk- and sensation seeking, spacial orientation, physical strength and higher rates in physical aggression. In combination with higher birth and accidental death rates this pattern might be a reflection of the systemic variational function (testing the boundaries of beneficial characteristics) of the male sex. As a result, psychological sex differences might be influenced by a global tendency within a species to expand its norm of reaction, but at the same time to preserve the beneficial properties of the species. Moreover, Trofimova<ref name=Trofimova/> suggested a "redundancy pruning" hypothesis as an upgrade of the ETS theory. She pointed out to higher rates of psychopathy, dyslexia, autism and schizophrenia in males, in comparison to females. She suggested that the variational function of the "male partition" might also provide irrelevance/redundancy pruning of an excess in a bank of beneficial characteristics of a species, with a continuing resistance to any changes from the norm-driven conservational partition of species. This might explain a contradictory allocation of a high drive for social status/power in the male sex with the their least (among two sexes) abilities for social interaction. The high rates of communicative disorders and psychopathy in males might facilitate their higher rates of disengagement from normative expectations and their insensitivity to social disapproval, when they deliberately do not follow social norms.

Some of these speculations have yet to be developed into fully testable hypotheses, and a great deal of research is required to confirm their validity.<ref>{{cite journal | last1 = O'Connell | first1 = H | year = 2004 | title = Evolutionary theory in psychiatry and psychology | journal = Irish Journal of Psychological Medicine | volume = 21 | issue = 1| pages = 37 | doi=10.1017/s0790966700008193| pmid = 30308732 | doi-access = free }}</ref><ref>{{cite journal |last1=Rose |first1=S. |year=2001 |title=Revisiting evolutionary psychology and psychiatry |journal=The British Journal of Psychiatry |volume=179 |pages=558–59 |doi=10.1192/bjp.179.6.558-b |pmid=11731363 |issue=6 |doi-access=free }}</ref>