Homosexuality and cognition

The hypothesis that there is a neurobiological basis for sexual orientation has received substantial attention recently - examples being the anatomical difference found in the brains of some male homoseuals; new evidence of a strong genetic role in homsexuality, and the association found between homosexuality and left-handedness. Now the hypothesis has gotten a boost from yet another direction - research bearing on sex differences in cognitive abilities.

Scientists at McMaster University in Ontario report in the latest issue of Psychoneuroendocrinology [whew!] that on measures of visual spatial ability where consistent differences have been observed between males and females, male homsexuals fall between the two sexes.
"It is as if, in some cognitive respects, they are neurologically a third sex," says neuroscientist Sandra Witelson, who co-authored the paper with psychologist Cheryl M McCormick (now at McGill University).

The researchers administered three tests of spatial ability (where males excel) and two measuring verbal fluency (where felales show a small advantage) to three groups of 38 subjects each: homosexual men, heterosexual men, and heterosexual women, "The cognitive pattern of homosexual men was significantly different from heterosexual men but not significantly different from that of heterosexual women," says Witerson. The results - like those from other studies on homosexuality - are consistent with the hypothesis that homosexuals are exposed to atypical levels of prenatal sex hormones.

In the spatial tests, heterosexual males had the highest scores, followed by homosexual males, and then females. This pattern was particularly pronoun ced among right-handers in a test where subjects had to visualize the water level in a tilted glass. In a measure of verbal fluence the order was reversed: Women scored highest, followed by the homosexuals, and then the heterosexual men.

Witelson believes that evidence fom anatomical, genetic, hormonal, and neuropsychological research is converging to suggest that "sexual orientation... is part of a larger constellation of cognitive attributes." She adds that all this may lead to an explanation for the "apparently greater prevalence and ability of homosexual men compared to heterosexual men in some professions." But the bewilderingly complex relationships between brain anatomy, prenatal sex hormones, handedness and homosexuality still need a lot more sorting out.