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Homosexual male probands with monozygotic cotwins, dizygotic cotwins, or adoptive brothers were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or when this was impossible, asking the probands. Of the relatives whose sexual orientation could be rated, 52% (29/56) of monozygotic(More)
We present an overview of behavioral genetics research on homosexual and heterosexual orientation. Family, twin, and adoptee studies indicate that homosexuality and thus heterosexuality run in families. Sibling, twin, and adoptee concordance rates are compatible with the hypothesis that genes account for at least half of the variance in sexual orientation.(More)
Homosexual female probands with monozygotic cotwins, dizygotic cotwins, or adoptive sisters were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or, when this was impossible, by asking the probands. Of the relatives whose sexual orientation could be confidently rated, 34 (48%) of 71(More)
Available evidence suggests that male homosexuality is both familial and somewhat heritable and that some cases may be caused by an X-linked gene. However, most studies have recruited subjects in a relatively unsystematic manner, typically via advertisements, and hence suffer from the potential methodological flaw of ascertainment bias due to volunteer(More)
We recruited 51 predominantly homosexual and 50 predominantly heterosexual men as index subjects for a family study of sexual orientation. The sexual orientation of siblings (115 sisters and 123 brothers) was ascertained in two ways: via interview with the index subjects and via interview of and/or mailed questionnaire to the siblings themselves. Index(More)
Many researchers interested in sexual orientation can be separated into two camps: The "lumpers," who try to reduce sexual classifications to as small a number of categories as possible, and the "splitters," who try to show differences among groups and individuals that make classification schemes increasingly difficult and/or intricate. We report factor(More)
Sexual orientation may be defined as the sustained erotic attraction to members of one's own gender, the opposite gender, or both--homosexual, heterosexual, or bisexual, respectively. Interest in sexual orientation is as old as the science of psychology, yet many fundamental issues remain unresolved. This article reviews research in the development and(More)
We asked whether homosexual and heterosexual men and women differ on standard measures of cognitive ability. Subjects were adults recruited for a family study of sexual orientation. They completed the Fy Scale of the California Psychological Inventory, a self-administered measure of psychological "femininity," and were given subtests of the Wechsler Adult(More)