A relationship between handedness and sexual orientation has been suggested but not verified by a number of researchers, who report that homosexual individuals are somewhat more likely to be non-right-handed than heterosexual individuals. The relationship between handedness and sexual orientation appears to exist within both sexes and may reflect the biological etiology of homosexuality.
Lalumière and colleagues conducted a meta-analysis using previously acquired data on handedness and sexual orientation, as earlier studies had rendered conflicting results. The meta-analysis included 20 studies involving 6,987 homosexual (6,182 men and 805 women) and 16,423 heterosexual (14,808 men and 1,615 women) participants. Using 20 comparisons between heterosexual and homosexual men and 9 comparisons between heterosexual and homosexual women, it was found that homosexuals were 39% more likely to be non-right-handed than heterosexuals, with figures of 34% and 91% for homosexual men and homosexual women, respectively.
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 homosexual women were found to be significantly more non-right-handed than heterosexual women (18% vs 10%), no significant differences were found between heterosexual and homosexual men with respect to hand preference.
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 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.
Blanchard et al. argued that 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 males. However, the same study indicates that non-right handed males 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 are 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."
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