Biology and sexual orientation INAH3 weight for the heterosexual male brains was significantly larger than for the heterosexual female brains, while the results for the gay male group were between those of the other two groups but not quite significantly different from either. The neuron count also found a male-female difference in INAH3, but found no trend related to sexual orientation. A 2010 study, Garcia-Falgueras and Swaab asserted that "the fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge.
Sexual Preference (book) Sexual Preference (book) Sexual Preference: Its Development in Men and Women (1981) is a book about the development of sexual orientation by the psychologist Alan P. Bell and the sociologists Martin S. Weinberg and Sue Kiefer Hammersmith, in which the authors reevaluate what were at the time of its publication widely held ideas about the origins of heterosexuality and homosexuality, sometimes rejecting entirely the factors proposed as causes, and in other cases concluding that their importance had been exaggerated. Produced with the help of the American National Institute of Mental Health, the study was a publication of the Institute for