Science and belief: psychobiological research on sexual orientation.

The dominant paradigm that generates support for biological theories of sexual orientation has profound conceptual flaws. Not only does it equate the motor patterns of copulation in rodents with sexual orientation in humans, it assumes that the brain regions that regulate these behaviors in rodents participate in governing sexual orientation in humans. Reports of sex differences in the rodent brain generate speculation concerning the existence of differences in the human brain associated not only with sex but also with sexual orientation. Thus, recent years have witnessed numerous attempts to demonstrate that the brains of homosexuals exhibit characteristics that are typical of the opposite sex. In some cases, these attempt have come decades after persuasive evidence suggested that the brain characteristic in question does not differ between the sexes in humans. If a particular feature on the human brain does not differ between men and women, the phrase "typical of the opposite sex" is meaningless. It is, then, illogical to argue-even from the perspective of the biologically deterministic paradigm-that the feature should be typical of the opposite sex in homosexuals. This paper analyzes the assumptions and evidence that support biologically deterministic theories of sexual orientation. It is concluded that support for these theories derives as much from their appeal to prevailing cultural ideology as from their scientific merit. This appeal may explain why seriously flawed studies pass readily through the peer review process and become incorporated rapidly into the biologically deterministic canon where they remain viable even when replication attempts repeatedly fail.