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Sexual Orientation. Key Concepts. Sexual orientation Preference for individuals of a specific sex Not necessarily expressed behaviourally Appears fluid rather than taxonomic Homosexual Same-sex sexual orientation
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Key Concepts • Sexual orientation • Preference for individuals of a specific sex • Not necessarily expressed behaviourally • Appears fluid rather than taxonomic • Homosexual • Same-sex sexual orientation • Although the term has a “clinical” significance to it, it remains useful for scientific areas of study
Related Information • Gender atypicality is common in adolescent and adult homosexual individuals • 2D:4D • Differences in sexual preferences and jealousy in “butch” vs. “femme” lesbians • Increased incidence of non-right handedness in homosexual individuals
Psychoanalytic Perspectives • According to Freud, all people are bisexual • Possible causes of homosexual orientation • Overly-powerful or ‘misdirected’ libido • Neurosis or perversion • Unresolved Oedipal complex • “Adaptational” perspective argues that homosexual individuals are afraid of the opposite sex, and so adapt by creating relationships with same sex individuals
Hormonal/Neurological Influences • Disruptions in rat hormonal processes affect differentiation of the hypothalamus • Lordosis & mounting • Human homosexual men demonstrate estrogen-feedback similar to that of women • Differences in INAH 3, anterior commissure, and suprachiasmatic nucleus in homosexual men vs. controls
Genetic Influences (1) • Twin & family studies have demonstrated some genetic relationship • Heritabilities range from .31-.74 in men & .27-.76 in women • The chromosomal region Xq28 has been linked to homosexual orientation in men, though it is hotly debated
Genetic Influences (2) • How could genes so obviously detrimental to fitness remain in the population? • Balanced superior heterzygote fitness (e.g., sickle cell anemia) • Kin selection (e.g., “sterile” castes) • Parent-offspring conflict over sibling fitness • Sex-linked benefits in females
Fraternal Birth Order Effect • Gualtieri & Hicks (1985) argued that fraternal birth order triggers an immunological response in the mother • Cantor et al. (2002) argue that each additional older brother increases the odds of homosexual orientation by 33% • Moreover, they argue that fraternal birth order affects the sexual orientation of approximately 1 in 7 gay men
Sexual Strategies • An interesting outcome of homosexual behaviour in groups is the removal of “strategic interference” • Homosexual men have, on average, a staggeringly large number of sexual partners, many of them strangers • Comparatively, homosexual women have very few sexual partners, and it is rare for any of them to be strangers
Homonegativity & Science • We have just reviewed some of the scientific evidence for a biological basis of sexual orientation, but what does it tell us about ourselves? • What is the appropriate use of this information? • Can a distinction between “learned” and “innate” orientation be used to defend or attack homosexuality?
The Wrap-Up • Defining sexual orientation • Gender atypicality, 2D:4D, handedness • Psychoanalytic perspectives • Hormonal & neurological influences • Genetic influences • Selectionist theories • Sexual strategies • Homonegativity & impact of science
Things to Come • ???