The cognitive, behavioral, and personality profiles of a male monozygotic triplet set discordant for sexual orientation.
The neurohormonal theory of sexual orientation proposes that homosexual men and homosexual women are exposed prenatally to a hormonal environment that is similar to that of the other sex. Prenatal exposure to an opposite-sex hormonal environment may lead the nervous system to develop in a manner consistent with the opposite sex. If this cross-sex exposure occurs, one prediction would be that the cognitive ability profile of homosexual men would be similar to that of heterosexual women. This study examined a set of male monozygotic triplets, aged 21 years, discordant for sexual orientation: 2 of the triplets were heterosexual, 1 was homosexual. The triplets were administered measures of 23 domains of cognitive ability, as well as measures of sexual orientation and masculinity/femininity. On the measures of cognitive ability, the triplets performed similarly, yet consistent differences were found between the 2 heterosexual triplets and the 1 homosexual cotriplet. Differences having the same pattern were found for the number of Schafer homosexuality signs on the Rorschach, and on a homosexuality scale derived from items on the Minnesota Multiphasic Personality Inventory--2 (MMPI-2). Responses from the homosexual triplet were in a more feminine direction than responses from his 2 heterosexual cotriplets on measures of masculinity-femininity, which included measures derived from Rorschach responses, the MMPI-2 Masculinity-Femininity scale, the Bem Sex Role Inventory, and the Boyhood Gender Conformity Scale. Responses to the 16 Personality Factor Questionnaire also distinguished the 1 homosexual triplet from the 2 heterosexual cotriplets. These findings support the view that the prenatal hormonal environment may have enduring effects on selected behavioral traits.
Hershberger
Scott L
SL
Department of Psychology, California State University, Long Beach 90840, USA. scotth@csulb.edu
Segal
Nancy L
NL
D000328:Adult; D003071:Cognition / Q000502:physiology; D005783:Gender Identity; D020010:Heterosexuality / Q000502:physiology; D006716:Homosexuality / Q000502:physiology; D006801:Humans; D008297:Male; D010555:Personality Inventory / Q000706:statistics & numerical data; D011594:Psychometrics; D011606:Psychosexual Development / Q000502:physiology; D012725:Sexual Behavior / Q000502:physiology; D011795:Surveys and Questionnaires; D014310:Triplets; D014430:Twins, Monozygotic