Download Psychology of Gender and Sex Differences

Psychology 320:
Psychology of Gender
and Sex Differences
Lecture 17
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Office Hour Invitations
October 23rd, 1:30-2:30, Kenny 2517
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Announcement
Jacqueline-Marie (TA for students with last names A-M)
must cancel her office hour today due to a missed airline
flight on return from a conference.
Please feel free to contact her with questions via e-mail
over the weekend or early next week.
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Biological Theories of Sex Differences
1. What biological theories have been proposed to
explain sex differences? (continued)
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By the end of today’s class, you should be able to:
1. review evidence that supports genetic contributions
to sex differences in psychological characteristics.
2. discuss the causes and symptoms of Klinefelter
syndrome.
3. identify the three classes of sex-related hormones.
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4. review evidence that supports hormonal contributions
to sex differences in psychological characteristics.
5. define the “challenge hypothesis.”
6. discuss the causes and symptoms of congenital
adrenal hyperplasia.
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What biological theories have been proposed to explain
sex differences? (continued)
2. Genetic Theories (continued)
 Example 2: Genetic Atypicalities
 Klinefelter Syndrome
• Results from an extra X chromosome in males (XXY).
• Incidence: 1/1000 – 3/1000 live births.
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• Physical symptoms include:
small firm testes
small penis
underdeveloped muscles
rounded body type (i.e.,
wide hips)
atypical body
proportions
tall build
gynecomastia
reduced facial/body hair
language learning impairment
decreased libido
infertility
epilepsy
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• Psychological symptoms include: “incomplete
masculinization” and “feminization.”
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3. Hormonal Theories
 There are three classes of sex-related hormones:
Estrogens (e.g., estradiol; relatively high among
females).
Progestins (e.g., progesterone).
Androgens (e.g., testosterone; relatively high among
males).
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 Estrogens and androgens are particularly important
in sex differentiation, in utero and at puberty.
 Research suggests, in addition to sex differentiation,
hormones influence the psychological and behavioural
characteristics of the sexes.
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 Example 1: Non-Human Animal Experiments
 vom Saal, Grant, McMullen, and Laves (1983)
• Contrasted the behaviour of male mice exposed to high
prenatal testosterone levels and male mice exposed to
low prenatal testosterone levels.
• Target embryos were “placed” between male siblings or
female siblings.
• Males exposed to higher testosterone levels
displayed more aggressive behaviour postnatally.
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 Example 2: Correlational Studies
 Dabbs, Carr, Frady, and Riad (1995);
Dabbs, Ruback, Frady, Hopper, and Sgoutas (1988)
• Found that male and female prison inmates who had
relatively high levels of testosterone displayed higher
levels of negative masculinity (e.g., impulsiveness,
aggression, disobedience; vs. positive masculinity).
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 Example 3: Meta-Analytic Studies
 Book, Starzyk, and Quinsey (2001)
• Conducted a meta-analysis of 45 studies that examined
the relationship between testosterone and aggression
among females and males.
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• Average correlation was +.23; correlation was
strongest among males aged 13 – 20 years, at +.58.
• The authors proposed the “challenge hypothesis” to
explain the latter finding.
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 Example 4: Hormonal Atypicalities
 Congenital Adrenal Hyperplasia (CAH)
• CAH is a genetically-based disorder that results in
excessive androgen production in utero.
• Male fetuses are relatively unaffected by CAH. Female
fetuses develop ”masculinized” genitalia.
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Congenital
Adrenal
Hyperplasia
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 Ehrhardt, Epstein, and Money (1968)
• Examined 15 girls diagnosed with CAH.
• The behavioural profiles of the CAH participants were
more “masculine” than those of controls, as indicated by:
lower levels of anticipation of marriage, preference for
career over marriage, less preference for doll play, less
interest in infant care, a preference for boy’s clothes, a
greater interest in outdoor activity.
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 Hines, Brook, and Conway (2004)
• Examined 16 women and 9 men diagnosed with CAH.
• CAH women recalled more male-typical play behavior,
reported less satisfaction with female sex assignment,
and showed less heterosexual interest than female
controls.
• CAH men did not differ significantly from male controls.
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Biological Theories of Sex Differences
1. What biological theories have been proposed to
explain sex differences? (continued)
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