Handedness and sexual orientation

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A relationship between handedness and sexual orientation has been suggested by a number of researchers, who report that heterosexual individuals are somewhat more likely to be right-handed than are homosexual individuals.

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The relationship between handedness and sexual orientation has been suggested within both sexes and may reflect the biological etiology of sexual orientation; work by Ray Blanchard has linked the relationship to the fraternal birth order effect, which suggests that a man with several older biological brothers is more likely to be homosexual.

Studies

Lalumière et al., 2000 meta-analysis

Lalumière et al. conducted a meta-analysis of 20 studies with a total of 6,987 homosexual and 16,423 heterosexual participants. They found that homosexual men had a 34% greater odds of not being right-handed, and homosexual women had a 91% greater odds (39% overall). [1]

Williams et al., 2000

In a study involving 382 men (278 homosexual and 104 heterosexual) no significant association emerged between handedness and sexual orientation. [2]

Mustanski et al., 2002 study

Mustanski et al. examined sexual orientation and hand preference in a sample of 382 men (205 heterosexual; 177 homosexual) and 354 women (149 heterosexual; 205 homosexual). Although a significantly higher proportion of homosexual women was found to be left-handed compared to heterosexual women (18% vs. 10%), no significant differences were found between heterosexual and homosexual men with respect to hand preference. [3]

Lippa, 2003 study

Lippa examined sexual orientation and handedness in a sample of 812 men (351 heterosexual; 461 homosexual) and 1,189 women (707 heterosexual; 472 homosexual). Homosexual men were 82% more likely to be non-right-handed than heterosexual men, but no significant differences were found between heterosexual and homosexual women in terms of handedness. When combining men and women into one large sample, homosexual individuals were 50% more likely to be non-right-handed than heterosexual individuals. [4]

Blanchard et al., 2006 study

Blanchard et al. argued that the fraternal birth order effect (the probability that a boy will be homosexual increases with the number of older brothers who have the same biological mother) appears to be limited to right-handed men. Moreover, the same study indicates that left-handed men without older brothers are more likely to be homosexual than non-right-handed men who have older brothers. [5] As Blanchard et al. said in their report,

The odds of homosexuality is higher for men who have a non-right hand preference or who have older brothers, relative to men with neither of these features, but the odds for men with both features are similar to the odds for men with neither. [5]

BBC survey

In a multinational online survey, it was found that gay men and lesbians are more likely to be left-handed (13 and 11%, respectively) than heterosexual men and women (11% and 10%, respectively). Bisexuals of both sexes more often described themselves as ambidextrous than gay or heterosexual individuals of the same sex (bisexual men: 12%; gay and heterosexual men: 8%; bisexual women: 16%; lesbians: 12%; heterosexual women: 8%). [6]

Blanchard, 2008 Archives of Sexual Behavior study

A subsequent study by Blanchard found that both right-handed homosexual men and left-handed heterosexual men had a statistically significant number of older male siblings, but that there was no significant observable effect either for right-handed heterosexual men or for left-handed homosexual men. [7]

Blanchard, 2008 Laterality study

Blanchard discussed ways in which the fraternal birth order effect and handedness could be explained in terms of the maternal immune hypothesis. In this, the mother is assumed to grow more immune to male antigens with each pregnancy, and thus produce a greater number of "anti-male" antibodies. He suggests two possibilities: Either that non-right-handed fetuses are less sensitive to the antibodies, or that the mothers of left-handed fetuses do not, for some reason, produce them. [8]

Schwartz et al., 2010 hair whorl study

In a sample including 694 gay men and 894 straight men, it was found that 13.9% of gay men and 15.9% of straight men were not right-handed, a non-significant difference. The study replicated the 'older brother effect' for homosexual men, but unlike Blanchard (2006) (see above), it found that the effect applied to both right-handed and left-handed gay men, being in effect stronger for the latter than for the former. [9]

Kishida and Rahman, 2015

In a sample of 478 heterosexual men and 425 homosexual men, gay men were found to show a significantly greater likelihood of extreme right-handedness and non-right-handedness compared to heterosexual men. [10]

Lee Ellis et al., 2016

Among a sample of university students in Malaysia and the United States, it was found that same-sex attraction was linked with left-handedness among women. Among men, no such correlation was found after controlling for ethnicity. [11]

Asexuality

A 2014 Internet study attempted to analyze the relationship between self-identification as asexual, handedness and other biological markers, in comparison to individuals of other sexual orientation groups. A total of 325 asexuals (60 men and 265 women), 690 heterosexuals (190 men and 500 women), and 268 non-heterosexuals (64 men and 204 women) completed online questionnaires. The study asserts that asexual men and women were 2.4 and 2.5 times, respectively, more likely to not be right-handed than their heterosexual counterparts. [12]

See also

Related Research Articles

Heterosexuality is romantic attraction, sexual attraction or sexual behavior between persons of the opposite sex or gender. As a sexual orientation, heterosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" to persons of the opposite sex; it "also refers to a person's sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions." Someone who is heterosexual is commonly referred to as straight.

Sexual orientation is an enduring pattern of romantic or sexual attraction to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender. These attractions are generally subsumed under heterosexuality, homosexuality, and bisexuality, while asexuality is sometimes identified as the fourth category.

The relationship between biology and sexual orientation is a subject of research. While scientists do not know the exact cause of sexual orientation, they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences. Hypotheses for the impact of the post-natal social environment on sexual orientation, however, are weak, especially for males.

Kinsey scale Scale for measuring sexual orientation

The Kinsey scale, also called the Heterosexual–Homosexual Rating Scale, is used in research to describe a person's sexual orientation based on one’s experience or response at a given time. The scale typically ranges from 0, meaning exclusively heterosexual, to a 6, meaning exclusively homosexual. In both the male and female volumes of the Kinsey Reports, an additional grade, listed as "X", indicated "no socio-sexual contacts or reactions". The reports were first published in Sexual Behavior in the Human Male (1948) by Alfred Kinsey, Wardell Pomeroy, and others, and were also prominent in the complementary work Sexual Behavior in the Human Female (1953).

Birth order

Birth order refers to the order a child is born in their family; first-born and second-born are examples. Birth order is often believed to have a profound and lasting effect on psychological development. This assertion has been repeatedly challenged. Recent research has consistently found that earlier born children score slightly higher on average on measures of intelligence, but has found zero, or almost zero, robust effect of birth order on personality. Nevertheless, the notion that birth-order significantly influences personality continues to have a strong presence in pop psychology and popular culture.

Estimates and variance for the lesbian, gay and bisexual (LGB) population are subject to controversy and debate. Obtaining precise numbers on demographics of sexual orientation is difficult for a variety of reasons, including the nature of the research questions.

Sexual attraction to transgender people has been the subject of scientific study and social commentary. Psychologists have researched sexual attraction toward trans women, cross dressers, non-binary people, and a combination of these. Cisgender men attracted to transgender women primarily identify as heterosexual and sometimes as bisexual, but rarely as homosexual. Sexual arousal research has confirmed that their response patterns are unlike those of gay men and resemble those of heterosexual men, except that they are highly aroused by transgender women in addition to cisgender women. They show little arousal to men. A substantial proportion of cisgender men attracted to transgender women report also experiencing autogynephilia, sexual arousal in response to the image of themselves as female. There has been some discussion of attraction to trans men, but it has not yet been the topic of scientific study.

Fraternal birth order has been correlated with male sexual orientation, with a significant volume of research finding that the more older brothers a male has from the same mother, the greater the probability he will have a homosexual orientation. Ray Blanchard and Anthony Bogaert first identified the association in the 1990s and named it the fraternal birth order effect. Scientists have attributed the effect to a prenatal biological mechanism, since the association is only present in men with older biological brothers, and not present among men with older step-brothers and adoptive brothers. The mechanism is thought to be a maternal immune response to male fetuses, whereby antibodies neutralize male Y-proteins thought to play a role in sexual differentiation during development. This would leave some regions of the brain associated with sexual orientation in the 'female typical' arrangement – or attracted to men. Biochemical evidence for this hypothesis was identified in 2017, finding mothers with a gay son, particularly those with older brothers, had heightened levels of antibodies to the NLGN4Y Y-protein than mothers with heterosexual sons.

Androphilia and gynephilia are terms used in behavioral science to describe sexual orientation, as an alternative to a gender binary homosexual and heterosexual conceptualization. Androphilia describes sexual attraction to men or masculinity; gynephilia describes the sexual attraction to women or femininity. Ambiphilia describes the combination of both androphilia and gynephilia in a given individual, or bisexuality.

Ray Blanchard American-Canadian sexologist

Ray Milton Blanchard is an American-Canadian sexologist, best known for his research studies on transsexualism, pedophilia and sexual orientation. He found that men with more older brothers are more likely to be gay than men with fewer older brothers, a phenomenon he attributes to the reaction of the mother's immune system to male fetuses. Blanchard has also published research studies on phallometry and several paraphilias, including autoerotic asphyxia.

Homosexual transsexual is a taxonomic category of transsexual individuals used in sexology, psychology, and psychiatry. It categorizes trans women who are exclusively attracted to men, and less often trans men who are exclusively attracted to women, based on their sex assigned at birth, rather than their current gender identity. The concept of categorizing trans women by sexual orientation originated with Magnus Hirschfeld in 1923, and was further developed by the sexologist Harry Benjamin in 1966 as a component of the Benjamin scale. The specific term homosexual transsexual was coined by Kurt Freund in 1973, and used from 1982 onward by him and others.

Blanchard's transsexualism typology is a proposed psychological typology of gender dysphoria, transsexualism, and fetishistic transvestism, created by Ray Blanchard through the 1980s and 1990s, building on the work of prior researchers, including his colleague Kurt Freund. Blanchard categorized trans women into two groups: homosexual transsexuals who are attracted exclusively to men, and who seek sex reassignment surgery because they are feminine in both behavior and appearance; and autogynephilic transsexuals who are sexually aroused at the idea of having a female body.

The study of the causes of transsexuality investigates gender identity formation of transgender people, especially those who are transsexual. Transgender people have a gender identity that does not match their assigned sex, often resulting in gender dysphoria. The causes of transsexuality have been studied for decades. The most studied factors are biological, especially brain structure differences in relation to biology and sexual orientation. Environmental factors have also been proposed.

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, while other researchers include biological influences such as prenatal hormones as part of environmental influences.

Sexual orientation is an enduring pattern of romantic or sexual attraction to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender, or none of the aforementioned at all. The ultimate causes and mechanisms of sexual orientation development in humans remain unclear and many theories are speculative and controversial. However, advances in neuroscience explain and illustrate characteristics linked to sexual orientation. Studies have explored structural neural-correlates, functional and/or cognitive relationships, and developmental theories relating to sexual orientation in humans.

Sexual fluidity is one or more changes in sexuality or sexual identity. Sexual orientation is stable and unchanging 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. There is no scientific evidence that sexual orientation can be changed through psychotherapy. Sexual identity can change throughout an individual's life, and may or may not align with biological sex, sexual behavior or actual sexual orientation.

The hormonal theory of sexuality holds that, just as exposure to certain hormones plays a role in fetal sex differentiation, such exposure also influences the sexual orientation that emerges later in the adult. Prenatal hormones may be seen as the primary determinant of adult sexual orientation, or a co-factor with genes, biological factors and/or environmental and social conditions.

LGBT demographics of the United States Total population of lesbian, gay, bisexual and transgender people in the United States

The demographics of sexual orientation and gender identity in the United States have been studied in the social sciences in recent decades. A 2017 Gallup poll concluded that 4.5% of adult Americans identified as LGBT with 5.1% of women identifying as LGBT, compared with 3.9% of men. A different survey in 2016, from the Williams Institute, estimated that 0.6% of U.S. adults identify as transgender.

Outline of LGBT topics Overview of and topical guide to LGBT topics

The following outline offers an overview and guide to LGBT topics.

References

  1. Lalumière, M.L.; Blanchard, R.; Zucker, K.J. (2000). "Sexual orientation and handedness in men and women: A meta-analysis". Psychological Bulletin. 126 (4): 575–592. doi:10.1037/0033-2909.126.4.575. PMID   10900997.
  2. Williams, Terrance J.; Pepitone, Michelle E.; Christensen, Scott E.; Cooke, Bradley M.; Huberman, Andrew D.; Breedlove, Nicholas J.; Breedlove, Tessa J.; Jordan, Cynthia L.; Breedlove, S. Marc (2000). "Finger-length ratios and sexual orientation" (PDF). Nature. 404 (6777): 455–456. doi:10.1038/35006555. PMID   10761903.
  3. Mustanski, B.S.; Bailey, J.M.; Kaspar, S. (2002). "Dermatoglyphics, handedness, sex, and sexual orientation". Archives of Sexual Behavior . 31 (1): 113–122. doi:10.1023/A:1014039403752. PMID   11910784.
  4. Lippa, R. (2003). "Handedness, sexual orientation, and gender-related personality traits in men and women". Archives of Sexual Behavior . 32 (2): 103–114. doi:10.1023/A:1022444223812. PMID   12710825.
  5. 1 2 Blanchard, R.; Cantor, J.; Bogaert, A.; Breedlove, S.; Ellis, L. (2006). "Interaction of fraternal birth order and handedness in the development of male homosexuality". Hormones and Behavior. 49 (3): 405–414. doi:10.1016/j.yhbeh.2005.09.002. PMID   16246335.
  6. "BBC – Science & Nature – Sex ID – Study Results".
  7. Blanchard, R. (2006). "Sex ratio of older siblings in heterosexual and homosexual, right-handed and non-right-handed men". Archives of Sexual Behavior . 37 (6): 977–981. doi:10.1007/s10508-006-9119-2. PMID   17186124.
  8. Blanchard, R. (2008). "Review and theory of handedness, birth order, and homosexuality in men". Laterality: Asymmetries of Body, Brain and Cognition. 13 (1): 51–70. doi:10.1080/13576500701710432. PMID   18050001.
  9. Gene Schwartz; et al. (2010). "Biodemographic and Physical Correlates of Sexual Orientation in Men". Archives of Sexual Behavior . 39 (1): 93–109. doi:10.1007/s10508-009-9499-1. PMID   19387815.
  10. Mariana Kishida; Qazi Rahman (2015). "Fraternal birth order and extreme right-handedness as predictors of sexual orientation and gender nonconformity in men". Archives of Sexual Behavior . 44 (5): 1493–1501. doi:10.1007/s10508-014-0474-0. PMID   25663238.
  11. Ellis, Lee; Skorska, Malvina N.; Bogaert, Anthony F. (2016). "Handedness, sexual orientation, and somatic markers for prenatal androgens: Are southpaws really that gay?". Laterality. 22 (2): 1–24. doi:10.1080/1357650X.2016.1151024. PMID   26932806.
  12. Yule MA, Brotto LA, Gorzalka BB (2014). "Biological markers of asexuality: Handedness, birth order, and finger length ratios in self-identified asexual men and women". Archives of Sexual Behavior . 43 (2): 299–310. doi:10.1007/s10508-013-0175-0. PMID   24045903.