Ken Zucker is the lead psychologist at Toronto’s Centre for Addiction and Mental Health. He received his Ph.D. from University of Toronto in 1982.
Is there evidence that sexual orientation is biologically determined?
I think if one looks at the collective body of evidence regarding the biology of sexual orientation, I think it would only be extreme dogmatists that would try to argue that there is no evidence that biological factors play a role in the differentiation of sexual orientation…I think there is some evidence that sexual orientation in males and sexual orientation in females has a heritable basis.
What can the science tell us in terms of linking gender non-conformity and sexual orientation?
We now know from a whole variety of retrospective data sets that one developmental marker or predictor of sexual orientation in both men and women pertains to a variable that some people refer to as gender non-conformity. Other people refer to it as gender variant behavior. Other people simply use the term sex-typed or gender typed behavior.
And a whole bunch of retrospective studies show that, on average, gay men and lesbian women recall engaging in more cross-sex typed behavior or gender non-conforming behavior or gender variant behavior. Whatever term one prefers, in childhood compared to the recollections of heterosexual men and women. And these differences were quite large and this has been documented repeatedly in numerous studies, spanning several decades. The studies are not limited to North America. There have been samples from Europe and in non-western cultures, etc.
So, one conclusion that I made that was based on retrospective data, patterns of gender behavior in childhood is a strong predictor of later sexual orientation. And my own sense in the scientific literature is that link now is accepted as being a strong link. Nobody, including myself, says that it is a perfect link, but it is a strong link.