Handedness and sexual orientation

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. The relationship between handedness and sexual orientation has been suggested within both sexes and may reflect the biological etiology of sexual orientation; recent 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. The theory is still tentative and not all research has been able to confirm the disparity between homosexual and heterosexual men.

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 non-right-handedness, 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 1189 women (707 heterosexual; 472 homosexual). Homosexual men were 82% more likely to be left-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 left-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. 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]

Bogaert, 2007 study

In a study of 373 of heterosexual and 538 gay or bisexual men, a link was found between non-heterosexual orientation and extreme right-handedness, but not left-handedness.^[7]

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 for right-handed heterosexual men or for left-handed homosexual men.^[8]

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; 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.^[9]

Rahman et al., 2009 hair whorl study

Two hundred men participated in the study, half straight and half gay. Scores on the Edinburgh Handedness Inventory indicated that 12% of straight men and 9% of gay men were left-handed, a non-significant difference.^[10]

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 non-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.^[11]

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.^[12]

Lee Ellis et al., 2016

Among a sample of university students in Malaysia and the US, 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.^[13]

Asexuality

A 2014 study attempting to analyze the biological markers of asexuality, asserts that non-sexual men and women were 2.4 and 2.5 times, respectively, more likely to be non-right-handed than their heterosexual counterparts. The study also found odds were 2.39 higher for left-handedness among homosexual and bisexual women compared to their heterosexual counterparts, but no significant differences between heterosexual, gay and bisexual men.^[14]

See also

• Handedness § Sexuality and gender identity
• Biology and sexual orientation
• Prenatal hormones and sexual orientation
• Transgender
• Laterality
• Digit ratio

References