1. Sexual Orientation
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2. Myth?
• Lesbians and gays are always trying to seduce heterosexuals.
• Gays and lesbians are oversexed.
• Bisexual have the best of both worlds.
• It’s easy to spot a gay or lesbian in a crowd.
• Within a relationship setting, gays and lesbians mimic traditional
heterosexual patterns.
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3. Sex Typical Behavior
• Do gay men prefer feminine males? Lesbians prefer masculine
females?
– Both gay men and lesbians tend to prefer sex-typical appearance
– preference less strong for feminine males
– no typical preference for sex-typical behavior among lesbians
(Bailey et al., 1997)
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4. Prevalence
• Alfred Kinsey (1953)
– exclusively heterosexual
• 75-85% males
• 80-90% females
– exclusively homosexual
• 4% males
• 2% females
– bisexual
• 10-15% males
• 8-10% females
• More recent studies have replicated these rates
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5. Homosexuality as a
Mental Illness
• DSM (1952): sociopathic personality disturbance
• DSM-R (1968): sexual deviation
• DSM-II (1973): ego-dystonic homosexuality
– Criteria for mental disorders:
• causes personal distress
• interferes with social effectiveness
• DSM-III and beyond
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6. Psychopathology
(Fergusson et al., 1999)
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7. Genetic Evidence
• Family studies
– homosexual females more likely to have homosexual brothers
(Bailey & Bell, 1993)
– brothers concordant for homosexuality were similar in childhood
gender nonconformity (Bailey, 2000)
– gender nonconformity inherited trait for both males and females
– 90% of gay or bisexual males had sons who were straight (Bailey,
1995).
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8. Genetic Evidence
• Twin studies
– 52% concordance identical twins (male)
– 22% concordance fraternal twins (male)
– 11% concordance for genetically unrelated brothers (Bailey &
Pillard, 1991)
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9. Genetic Evidence
• Sex - linked?
– X-linked
– Xq28 region
• Some studies indicate homosexuality on both maternal and paternal
sides (Bailey et al., 1999)
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10. Brain Anatomy Evidence
• Hypothalamic differences:
– suprachiasmatic nucleus (SCN) larger and has more cells in gay
men (Swaab, 1990)
– INAH1-4 regions (Simon LeVay, 1991)
• examined homosexual men, heterosexual men and women
• area INAH3 differentiated groups
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11. Hormone & Prenatal Evidence
• Prenatal
– exogenous hormone administration
• DES
– H-Y antigen
– maternal stress
– testosterone levels
• handedness
• otoacoustic emissions (OAEs)
• finger lengths, 2d:4d
• Testosterone levels in adulthood
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12. Birth Order
• Latter born sons more likely to be gay
• Mothers develop immunity to H-Y Antigen
(Blanchard, 2001 )
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13. Behavioral Measures
• Gay men on average better at spatial rotation than gay women
• Gay men more aggressive and competitive than gay women
• Straight men more aggressive and competitive than gay men
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14. Homosexuality & Evolution
How can a trait that seems to inhibit the
likelihood of offspring remain in the
population?
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15. Homosexuality & Evolution
• balanced polymorphism
• biological exuberance
• reciprocal altruism - same sex alliances
• kin-selection
(Miller, 2000)
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16. Sex Differences in
Sexual Orientation
• Is it a phase?
– Men - hard wired
– Lesbian and bisexual young women were followed over a 5 year
period (Diamond, 2003)
• Over a quarter relinquished their gay identity
– More likely to indicate attraction to both men and women
– indicated that degree of attraction to men and women did
not significantly Change
– 1 women described lesbian period as “a phase”
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17. Sex Differences in
Sexual Orientation
• Sex differences in sexual arousal patterns (Chivers et al., in press)
– examined gay and straight men and women, and male to female
transsexuals
– viewed male/male, female/female, and male/female erotica
– gathered physiological and subjective data
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18. Legal Issues
• Antisodomy laws
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19. Antisodomy Laws
• Sec. 21.01. Definitions.
(1) "Deviate sexual intercourse" means:
(A) any contact between any part of the genitals of one person
and the mouth or anus of another person; or
(B) the penetration of the genitals or the anus of another person
with an object.
• Sec. 21.06. Homosexual Conduct.
(a) A person commits an offense if he engages in deviate sexual
intercourse with another individual of the same sex.
(b) An offense under this section is a Class C misdemeanor. ($500)
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20. Legal Issues
• Antisodomy laws
• Gay parents & gay adoption
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21. Gay Parents &
Children of Gay Parents
• Comparing gay and straight parents (e.g., Allen & Burrell, 1996).
– Parental data:
• parent’s rating of parent/child interaction
• parental attitude about sexual development
• rating of child’s level of satisfaction
• teacher’s rating of child’s school behavior
– Child data:
• sexual orientation
• life satisfaction
• cognitive development
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22. Gay Parents &
Children of Gay Parents
• Children of gay parents highly likely to report that their problems are
related to their parent being gay (94%)(Cameron & Cameron, 2002)
• Children of gay parents equally likely to be teased, but teased about
family (e.g., Vanfraussen et al., 2002)
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23. Gay Adoption
• Do adoption agencies allow gay adoption?
– 823 adoption agencies contacted, 26% responded (Brodzinsky et
al., 2002)
– of these:
• 63% accepted applications from gay couples
• 38% had made at least one gay adoption
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24. Legal Issues
• Antisodomy laws
• Gay parents & gay adoption
• Gay marriage
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