Prenatal hormones and sexual orientation Only 23% of childhood gender problems will result in transsexuality in adulthood. Drawing on some transsexualism cases, Garcia-Falgueras and Swaab state that "[f]rom these examples it appears that the direct action of testosterone on the developing brain in boys and the lack of such action on the developing brain in girls are crucial factors in the development of male and female gender identity and sexual orientation ... ." Countless studies have been run on peripheral levels of sex steroids in male and female homosexuals, a considerable number of which claimed to find "less 'male hormone' and/or more 'female hormone' in
Sexual Preference (book) that while Bell "et al."′s suggestion that biological factors have a stronger influence on exclusive homosexuality than they have on bisexuality may seem plausible, it has not been directly tested and appears to conflict with available evidence, such as that concerning prenatal hormone exposure. The psychologist Bruce Rind credited Bell "et al." with disproving psychoanalytic theories about the development of homosexuality, along with the idea that childhood seduction causes homosexuality. The psychologist Mark Yarhouse wrote that while "Sexual Preference" is cited by proponents of a biological explanation, it relies on retrospective memory recall, which can be unreliable. The psychologist J.