Neurohormonal functioning and sexual orientation: A theory of homosexuality–heterosexuality.

Abstract

Following a historical sketch of attempts to explain homosexuality, we review evidence indicating that the process of determining human sexual orientation is fundamentally the same in all mammals. In this process, four phenotypic dimensions of sexuality develop from two more or less distinct sex genotypes. Studies are reviewed that indicate how phenotypic deviations from these two genotypes (called sexual inversions) can occur. The causes of sexual inversions are categorized as genetic-hormonal, pharmacological, maternal stress, immunological, and social experiential. From this evidence, we propose a theory of how the entire spectrum of human sexual orientation (vs. simply homosexuality) is determined.A consistent preference for sexual relations with one's own sex (homosexuality), the opposite sex (heterosexuality), or vary-

Sexual orientation related differences in spatial memory

“…These findings add to growing evidence for cross-sex shifts in the neuropsychological profiles of homosexual males as predicted by the theory of neurohormonal differentiation (Ellis & Ames, 1987). They have parallels to prior work demonstrating female-typical performance by homosexual males in other cognitive functions, such as poorer scores on mental rotation and improved verbal abilities (Gladue et al, 1990;Hall & Kimura, 1995;McCormick & Witelson, 1991;Neave et al, 1999a;Sanders & Ross-Field, 1987;Wegesin, 1998a).…”

“…These have been generated primarily by the theory of neurohormonal sexual differentiation, in which the neurodevelopment of physiological and behavioral differences between males and females is proposed to be under the control of gonadal sex steroids. Homosexuals are considered to follow sex-atypical patterns of development in partner preferences and sexually dimorphic neuropsychological functioning (Ellis & Ames, 1987;LeVay, 1993). Homosexual males and females show robust sexatypical shifts in retrospective and prospective childhood play interests and behavior and gender role orientation, and there is strong evidence to show similar shifts in cognitive functioning, neuroanatomical variation in hypothalamic and callosal regions, and neurophysiological activity in homosexual males (Alexander & Sufka, 1993;Bailey & Zucker, 1995;LeVay, 1991;Lippa, 2000;Sanders & Ross-Field, 1987;Reite et al, 1995;Scamvougeras et al, 1994).…”

Gender and Sexual Orientation Differences in Cognition Across Adulthood: Age Is Kinder to Women than to Men Regardless of Sexual Orientation

“…If males do show greater age-related decline than females, and if non-heterosexuals' cognitive performance is more like that of the opposite gender, then this raises the interesting question of whether age-related decline is not only associated with gender but also with sexual orientation. This would be in line with considerable evidence that sexual orientation differences in somatic, cognitive, and behavioral traits mimic those between women and men such that these traits in male homosexuals resemble (or are shifted toward) those in female heterosexuals and traits in female homosexuals resemble those in male heterosexuals; these effects are thought to be due in part to the relative feminization and masculinization, respectively, of the brain by prenatal hormones (Ellis & Ames, 1987). Another reason to suppose that sexual orientation may play a role follows from evidence that non-heterosexuals of both genders are vulnerable populations, for example, in terms of poorer mental and physical health in comparison with heterosexuals (De Graaf, Sandfort, & ten Have, 2006; lesbian elders" (Allen, 2005) and as far as we are aware, there have been no previous investigations of age-related decline in cognition as a function of sexual orientation.…”

Are 2D:4D finger-length ratios related to sexual orientation? Yes for men, no for women.

“…Although there may be different neural critical periods for various kinds of sex-typed behaviors (e.g., sex-typed play, aggression, sexual behaviors), neurohormonal theories of sexual orientation generally focus on effects from the 2nd to 5th months of gestation (Ellis & Ames, 1987), and they propose that androgens likely have organizational effects on sexually dimorphic structures in subcortical regions of the developing brain that are responsible for sexual behaviors (e.g., regions of the hypothalamus; see Byne et al, 2001;LeVay, 1991).…”

“…Complicating Robinson and Manning's results, however, was the additional finding that exclusively homosexual men had higher (more female-typical) 2D:4D ratios than nonexclusively homosexual and bisexual men. Manning (2002) noted that some theories argue that unusually high prenatal androgen exposure in males can lead to homosexuality (Geschwind & Galaburda, 1985a, 1985b, whereas others have argued just the opposite (Ellis & Ames, 1987). Complicating matters further, some theories argue that stress-induced testosterone surges in one period of fetal development may be followed by abnormal declines in later periods (e.g., James, 1989), and this may produce seemingly paradoxical effects-that is, characteristics associated with high testosterone levels in one period (e.g., low 2D:4D ratios) could then sometimes become associated with characteristics that are associated with low testosterone levels in another critical period (e.g., male homosexuality).…”