Environment and sexual orientation
The relationship between the environment and sexual orientation is a subject of research. In the study of sexual orientation, some researchers distinguish environmental influences from hormonal influences,[1] while other researchers include biological influences such as prenatal hormones as part of environmental influences.[2]
Scientists do not know the exact cause of sexual orientation, but they theorize that it is the result of a complex interplay of genetic, hormonal, and environmental influences.[1][3][4] They do not view sexual orientation as a choice.[1][3][5]
Evidence for the impact of the post-natal social environment on sexual orientation is weak, especially for males.[6] There is no substantial evidence which suggests parenting or early childhood experiences influence sexual orientation,[7][8] but research has linked childhood gender nonconformity and homosexuality.[9][10]
Sexual orientation compared with sexual orientation identity[edit]
Often, sexual orientation and sexual orientation identity are not distinguished, which can impact accurately assessing sexual identity and whether or not sexual orientation is able to change; sexual orientation identity can change throughout an individual's life, and may or may not align with biological sex, sexual behavior or actual sexual orientation.[11][12][13] Sexual orientation is stable and unlikely to change for the vast majority of people, but some research indicates that some people may experience change in their sexual orientation, and this is more likely for women than for men.[14] The American Psychological Association distinguishes between sexual orientation (an enduring attraction) and sexual orientation identity (which may change at any point in a person's life).[15] Scientists and mental health professionals generally do not believe that sexual orientation is a choice.[1][5]
The American Psychological Association states that "sexual orientation is not a choice that can be changed at will, and that sexual orientation is most likely the result of a complex interaction of environmental, cognitive and biological factors...is shaped at an early age...[and evidence suggests] biological, including genetic or inborn hormonal factors, play a significant role in a person's sexuality".[3] They say that "sexual orientation identity—not sexual orientation—appears to change via psychotherapy, support groups, and life events".[15] The American Psychiatric Association says that individuals may "become aware at different points in their lives that they are heterosexual, gay, lesbian, or bisexual" and "opposes any psychiatric treatment, such as 'reparative' or 'conversion' therapy, which is based upon the assumption that homosexuality per se is a mental disorder, or based upon a prior assumption that the patient should change his/her homosexual orientation". They do, however, encourage gay affirmative psychotherapy.[16]
Childhood gender nonconformity[edit]
Researchers have found childhood gender nonconformity (CGN) to be the largest predictor of homosexuality in adulthood.[9][10][34] Gay men often report being feminine boys, and lesbian women often report being masculine girls. In men, CGN is a strong predictor of sexual orientation in adulthood, but this relationship is not as well understood in women.[35][36][37] Women with congenital adrenal hyperplasia (CAH), which effects production of sex steroids, report more male typical play behaviors and show less heterosexual interest.[38] Bailey believes childhood gender nonconformity to be a clear indicator that male homosexuality is an inborn trait – the result of hormones, genes and other prenatal developmental factors. Bailey says boys are "punished much more than rewarded" for their gender nonconformity, and that such behavior "emerges with no encouragement, and despite opposition", making it "the sine qua non of innateness". Bailey describes gender nonconforming boys as the "poster children for biological influences on gender and sexuality, and this is true whether or not we measure a single biological marker".[39]
Daryl Bem proposed the "exotic becomes erotic" theory (EBE) in 1996. Bem argues that biological factors, such as prenatal hormones, genes and neuroanatomy, predispose children to behave in ways that do not conform to their sex assigned at birth.[40] Gender nonconforming children will often prefer opposite-sex playmates and activities. These become alienated from their same-sex peer group. As children enter adolescence "the exotic becomes erotic" where dissimilar and unfamiliar same-sex peers produces arousal, and the general arousal become eroticized over time.[41] Wetherell et al. state that Bem "does not intend his model as an absolute prescription for all individuals, but rather as a modal or average explanation."[40]
Two critiques of Bem's theory in the journal Psychological Review concluded that "studies cited by Bem and additional research show that Exotic Becomes Erotic theory is not supported by scientific evidence."[42] Bem was criticized for relying on a non-random sample of gay men from the 1970s and for drawing conclusions that appear to contradict the original data. An "examination of the original data showed virtually all respondents were familiar with children of both sexes", and that only 9% of gay men said that "none or only a few" of their friends were male, and most gay men (74%) reported having "an especially close friend of the same sex" during grade school.[42] Further, "71% of gay men reported feeling different from other boys, but so did 38% of heterosexual men. The difference for gay men is larger, but still indicates that feeling different from same-sex peers was common for heterosexual men." Bem also acknowledged that gay men were more likely to have older brothers (the fraternal birth order effect), which appeared to contradict an unfamiliarity with males. Bem cited cross-cultural studies which also "appear to contradict the EBE theory assertion", such as the Sambia tribe in Papua New Guinea, who segregate boys from females during adolescence and ritually enforce homosexual acts among teenagers (they believe this is important for male growth potential), yet once these boys reached adulthood, only a small proportion of men continued to engage in homosexual behaviour - similar to levels observed in the United States.[42] LeVay has said while the theory was ordered in a "believable order",[43]: 65 the theory "lacks empirical support".[43]: 164 Social psychologist Justin Lehmiller stated that Bem's theory has received praise "for the way it seamlessly links biological and environmental influences" and that there "is also some support for the model in the sense that childhood gender nonconformity is indeed one of the strongest predicators of adult homosexuality", but that the validity of the model "has been questioned on numerous grounds and scientists have largely rejected it."[44]
In 2003, Lorene Gottschalk, a self-described radical feminist suggested there may be a reporting bias within the links between gender nonconformity to homosexuality in literature.[45] Researchers have explored the possibility of bias by comparing childhood home videos with self-reports of gender nonconformity, finding that the presence of gender nonconformity was highly consistent with self-reporting, emerged early and carried into adulthood.[10]
Family and upbringing[edit]
General[edit]
Hypotheses for the impact of the post-natal social environment on sexual orientation are weak, especially for males. There is no substantial evidence which suggests parenting or early childhood experiences influence sexual orientation. Research has linked early childhood gender nonconformity and homosexuality; gay men, on average, have been observed to be significantly more feminine from early childhood while lesbians are significantly more masculine. Bisexuals also report childhood gender nonconformity, but the difference is not as large as it is for gay men and lesbians. Early gender nonconformity is suggestive evidence that non-heterosexual orientations are dependent on early biological factors (genetic influence, prenatal hormones, or other factors during fetal development), since this sex atypical behavior emerges despite no encouragement from the social environment or parents. Parents and adults may react negatively to this gender nonconformity in their children, resulting in higher rates of maltreatment. Early hypotheses presumed that childhood maltreatment experienced by some non-heterosexuals was the cause of non-heterosexual orientations, a theory which has not been supported by more thorough examination.[6]
Chemical disruptors[edit]
Environmental compounds such as plastic softeners (phthalate esters), which are pervasive environmental chemicals with anti-androgenic effects may interfere with sexual differentiation of the human brain during prenatal development.[56] Researchers are investigating exposure to these endocrine disruptors during pregnancy and later sexual orientation of offspring, although scientists caution that no conclusions can be made yet.[56][57][58] Historical records indicate homosexual people were present and recognized in many times, cultures and places prior to industrialisation.[6]
Between 1939 and 1960, around two million expectant mothers in the United States and Europe were prescribed a synthetic estrogen known as diethylstilbestrol (DES) in the belief that it would prevent miscarriages. DES did not prevent miscarriage, but it reportedly increased the likelihood of bisexuality and homosexuality in the daughters of women given the drug.[17][59]
Other[edit]
Data scientist Seth Stephens-Davidowitz reported that the actual prevalence of gay men does not appear to vary between states in the U.S. because the percentage of Internet porn searches that are for gay male porn are nearly the same in all states, about 5%. On this basis he believes migration of gay men to cities is overstated, and says that in states where there is a social stigma against homosexuality so that "many more gay men are in the closet than are out".[60][43]: 9