Sexual Orientation and the Brain: Does Biology Affect Homosexuality

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Sexual Orientation and the Brain Does Biology
Affect Homosexuality?

• By Alexandra and Ashley Dolhun

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Research Foundation

• Jagoses Queer Theory
• Essentialism vs. Constructionism
• Homosexuality
• Is sexual identity innate or is it the
  effect of social conditioning?

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Homosexuality The Biological Side

• Genetic influences on the brain
• Hormonal effects prenatal through adolescence
• Family Studies

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Genes

• Simon Levay
• Hypothesis Genetics involved in sexual
  orientation
• Studied Hypothalamus

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Results

• -Hypothalamus size differed in gay men
• -It doesnt prove homosexuality but brain
  structure may influence orientation

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Arguments of LeVays Research

• Disease/Medication Did it have an affect on
  brains?
• Sexual preference could have altered their
  brains, not genes

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Does a Gay Gene Exist?

• Dean Hamer led study
• 65 of gay brothers shared this marker with their
  straight brothers
• Results Study does not indicate having a
  certain gene will produce homosexuality, but may
  influence a persons sexual orientation

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Twins and Homosexuality

• Two recent studies on twins
• Fred Whitman of ASU
• Michael Bailey and Richard Pillard of
  Northwestern

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Concordance Rates in Twins

• Monozygotic Twins
• Dizygotic Twins
• Cause
• Prenatal environment differs

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Bailey and Pillard on Twins

• Researched females
• If one twin is gay is the other?
• Identical Twins- 48 chance
• Fraternal Twins-16

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Arguments on Bailey/Pillard Study

• Some twins tested at a young age, sexuality might
  still be in question
• Might not respond to entire population
• Cause of homosexuality in twins may differ from
  singletons

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Study of Brothers-Jerome Burne (2000)

• Birth Order
• Number of Sexual Partners
• Higher prevalence of androgens in gay men

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Lesbian Studies

• Marc Breedlove used 720 subjects
• Study Is finger length directly related to
  sexuality?
• All types tested

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Finger Length in Lesbians

• Lesbians have longer ring finger compared to
  index finger
• Lesbians have hands similar to males
• Difference believed to represent the effects of
  prenatal testosterone

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Inner Ears of Lesbians

• Study looked at ear structure in gay and straight
  women
• Difference in Cochlea
• Advice to girls watch those Q-tips!

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Genetic and Hormonal Anomalies- Causes of
homosexuality??

• Androgen insensitivity syndrome
• Males insensitive to androgen, responsive to
  estrogen
• Result
• Female phenotype
• Increased feminization of brain

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(Late Onset) Congenital Adrenal Hyperplasia

• Born female, exposed to excess androgens in the
  womb
• Several effects
• Enlarged clitoris or growth of penis
• Behavioral effects
• High degree in tomboyishness (dress, games, toys)
• Explanation brain becomes masculinized, thus
  changing behavior

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Genetic Dimorphisms

• Hermaphroditism
• Hormones affect body
• Child/Adult becomes intersexed
• In some cases, doctors reassign the sex at birth

• XXY Syndrome
• Males born with extra X chromosome
• Sexed as male with underdeveloped genitals
• May develop breasts

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Environment is a Factor

• Culture plays a big role in shaping personality,
  decisions, even sexuality
• Role models, musicians, television, friends are
  all forms of persuasion (Myers, 2002)

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Any Questions?