Functional cerebral asymmetry and sexual orientation in men and women.
Functional cerebral asymmetry was assessed in 32 gay men and 32 heterosexual men and in 30 lesbians and 30 heterosexual women with a linguistic dichotic listening test. All groups showed the typical greater right-ear accuracy and, by inference, left-hemisphere representation for language functions. As shown repeatedly in previous studies (e.g., M. P. Bryden, 1982), among heterosexuals, consistent-right-handers showed greater perceptual asymmetry than did non consistent-right-handers. In contrast, gay men and lesbians did not show an association between hand preference and magnitude of perceptual asymmetry. The results indicate different patterns of functional cerebral asymmetry in gay men and lesbians compared with heterosexual people and specifically, less association between motoric and linguistic components of cerebral asymmetry. This suggestion of atypical patterns of functional asymmetries is consistent with previous results of an increased prevalence of left-hand preference among gay men and lesbians compared with the heterosexual population (C. M. McCormick, S. F. Witelson, & E. Kingstone, 1990; C. M. McCormick & S. F. Witelson, 1991). The finding of an association between aspects of functional asymmetry, a neurological characteristics likely present from birth, and sexual orientation suggests that a neurobiological factor is involved in the origins of sexual orientation.