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.
Department of Psychology, California State University, Long Beach 90840, USA. scotth@csulb.edu
Scott L
SL
Hershberger
Nancy L
NL
Segal
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