1 Psychology 320: Psychology of Gender and Sex Differences Lecture 17

2 Office Hour Invitations October 23 rd, 1:30-2:30, Kenny

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 over the weekend or early next week. 3 Announcement

4 Biological Theories of Sex Differences 1. What biological theories have been proposed to explain sex differences? (continued)

5 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. 3. identify the three classes of sex-related hormones. 2. discuss the causes and symptoms of Klinefelter syndrome.

6 6. discuss the causes and symptoms of congenital adrenal hyperplasia. 5. define the “challenge hypothesis.” 4. review evidence that supports hormonal contributions to sex differences in psychological characteristics.

7 Results from an extra X chromosome in males (XXY). Klinefelter Syndrome Incidence: 1/1000 – 3/1000 live births.  Example 2: Genetic Atypicalities 2. Genetic Theories (continued) What biological theories have been proposed to explain sex differences? (continued)

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9 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

10 Psychological symptoms include: “incomplete masculinization” and “feminization.”

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14  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). 3. Hormonal Theories

15  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.

16  Example 1: Non-Human Animal Experiments Contrasted the behaviour of male mice exposed to high prenatal testosterone levels and male mice exposed to low prenatal testosterone levels. vom Saal, Grant, McMullen, and Laves (1983) Target embryos were “placed” between male siblings or female siblings. Males exposed to higher testosterone levels displayed more aggressive behaviour postnatally.

17 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).  Example 2: Correlational Studies

18  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.

19 Average correlation was +.23; correlation was strongest among males aged 13 – 20 years, at The authors proposed the “challenge hypothesis” to explain the latter finding.

20  Example 4: Hormonal Atypicalities CAH is a genetically-based disorder that results in excessive androgen production in utero. Congenital Adrenal Hyperplasia (CAH) Male fetuses are relatively unaffected by CAH. Female fetuses develop ”masculinized” genitalia.

21 Congenital Adrenal Hyperplasia

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23 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.

24 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.

25 Biological Theories of Sex Differences 1. What biological theories have been proposed to explain sex differences? (continued)