Hand preference, sexual preference and transsexualism
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Hand preference, sexual preference and transsexualism

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    Hand preference, sexual preference and transsexualism Hand preference, sexual preference and transsexualism Document Transcript

    • • Hand Preference, Sexual Preference and Transsexualism• Journal article by Richard Green, Robert Young; Archives of Sexual Behavior, Vol. 30, 2001 Hand Preference, Sexual Preference, and Transsexualism by Richard Green , Robert Young Richard Green (1,2,4) Robert Young (3) Atypical handedness patterns, i.e., persons being less exclusively right-handed, have been found previously in large samples of male and female homosexuals and in small samples of male and female transsexuals compared to controls. The posited role of prenatal androgen influencing both cerebral hemispheric dominance and psychosexual development warrants further study with large samples of transsexuals. 443 male-to- female transsexuals and 93 female-to-male transsexuals were studied for their use of the right or left hand in six common one-handed tasks. Both male and female transsexuals were more often non right-handed than male and female controls were. Results suggest an altered pattern of cerebral hemispheric organisation in male and female transsexuals. KEY WORDS: handedness; cerebral dominance; transsexualism; homosexuality. Handedness or hand use preference has been observed as early as Week 15 of gestation (Hepper et al., 1991). It may be influenced by prenatal androgen levels. One suggestion is that elevated levels of testosterone, perhaps during the second trimester of pregnancy, affect foetal brain development and increase asymmetry via accelerating the growth of the right hemisphere resulting in nonright-handedness (Galaburda et al., 1987; Geschwind and Galabruda, 1985a,b). In partial support, persons with known atypical prenatal sex hormone levels show alterations in handedness. Females with congenital adrenal hyperplasia, with elevated prenatal androgen, show increased nonright-handedness (Nass et al., 1987), as do females with intrauterine exposure to diethylstilbestrol (DES), a masculinising synthetic oestrogen (Schacter, 1994). However, Klinefelter syndrome (karyotype XXY) males show a high proportion of left-handers (Netley and Rovet, 1982) but have a postnatal, and perhaps prenatal, deficiency of androgen. Alternative mechanisms accounting for handedness include genetic models and range from single to multiple gene models (Annett, 1985; Jones and Martin, 2000). Another proposes two mechanisms by which individuals may become left-handed; natural or genetic left-handedness and pathological left-handedness, a consequence of diffuse neurodevelopmental difficulty. Elevated rates of birth stressors such as Rh incompatibility, higher rates of caesarean sections at birth and multiple births are associated with left-handedness (Coren, 1995). Left-handedness is associated with indicators of reduced Darwinian fitness such as a smaller number of offspring, lower birth weight and shorter life span (Yeo et al., 1993) and is found more commonly in persons with mental retardation, autism, schizophrenia, cerebral palsy, and epilepsy (Coren, 1993a). It is found more commonly in association with indicators of developmental instability such as fluctuating asymmetry of bilateral body features expected to be symmetrical, e.g. finger length (Yeo and Gangestad, 1998). Fluctuating asymmetry can result from