Handedness and sexual orientation.

Surveys of handedness distribution (i.e., the distribution across handedness categories in large samples, typically based upon self-reported right-, mixed- and left-handed classification) indicate approximately 90% of the population is right-handed (Springer & Deutsch, 1989). This distribution toward right-handedness has been called right shift based on a genetic model (Annett, 1985). The present study examined possible handedness distribution differences between 141 gay, lesbian, and bisexuals and 260 heterosexuals who have a homosexual/bisexual first-degree (biological) relative. Based on a five-category self-assessment handedness questionnaire that was validated using Briggs and Nebes' (1975) reformulation of Annett's inventory (1970), non-heterosexuals showed a reduction of right shift compared to heterosexuals (i.e., a population shift toward mixed- and left-handedness), confirming the results of Lindesay (1987) and Becker et al., (1989). Sexual orientation also weakly predicted handedness. The findings indirectly support the hypothesis of Geschwind and Galaburda (1985a, 1985b) that sexual orientation and handedness may be linked, both possibly influenced prenatally by testosterone. The discussion emphasizes (a) the meaninglessness in distinguishing genetic from hormonal influences and (b) non-heterosexually biased assumptions about human sexuality.