1 Psychology 320: Gender Psychology Lecture 17

2 Invitational Office Hour Invitations, by Student Number for October 22 nd 11:30-1:30, 3:30-4:30 Kenny

3 Midterm October 25: 30 multiple choice questions (1 point each). October 27: 5-6 short answer questions (2-6 points each, totaling 20 points). The exam is worth 20% of your final grade. The exam will be scored out of 50 points.

4 Please arrive on time to facilitate rapid distribution of the exams. Bring a pencil, eraser, pen, and your student ID to the exam. All electronic devices must be put away. Students may not leave the exam room during the last 10 minutes of the exam. Hats (e.g., baseball caps) should not be worn during the exam.

5 Biological Theories of Gender Differences 1. What biological theories have been proposed to explain gender differences? (continued)

6 By the end of today’s class, you should be able to: 1. review evidence that supports hormonal contributions to sex differences in psychological characteristics. 3. identify differences in the neuroanatomical features of the female brain and the male brain. 2. define the “challenge hypothesis.”

7 3. Hormonal Theories (continued) What biological theories have been proposed to explain gender differences? (continued)

8 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 were more likely to have committed violent crimes prior to their incarceration and were more likely to engage in unprovoked violence and rule infractions while in prison.  Example 2: Correlational Studies

9 Conducted a meta-analysis of 45 studies that examined the relationship between testosterone and aggression among males and/or females. Book, Starzyk, and Quinsey (2001)  Example 3: Meta-Analytic Studies Average correlation was +.23; correlation was strongest among males aged 13 – 20 years, at The challenge hypothesis has been proposed to explain the latter finding.

10  Example 4: Hormonal Abnormalities 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. However, female fetuses develop ”masculinized” genitalia

11 Congenital Adrenal Hyperplasia

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13 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, and a greater interest in outdoor activity. Referenced in Lecture 5.

14 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.

15 4. Neuroanatomical Theories  Sex differences have been identified in the structure of the brain.  Example 1: Interhemispheric Differences The functions of the brain are “lateralized.”

16 The brain areas responsible for language production and comprehension, mathematics, and analytical reasoning are largely located in the left hemisphere. The brain areas responsible for visual-spatial problem solving, facial and pattern recognition, perceptual and nonverbal skills, and musical ability are largely located in the right hemisphere.

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18 The results of a number of studies studies suggest that male brains are more lateralized than female brains: Voyer (1996): Conducted a meta-analysis of 396 studies; revealed greater brain lateralization among males than females for both linguistic abilities and visual-spatial abilities.

19 Notably, however, some studies (e.g., Sommer et. al., 2004) have failed to demonstrate sex differences in brain lateralization. Sex differences in performance on verbal tasks and visual-spatial tasks have been attributed to sex differences in brain lateralization.

20  Example 2: Hemispheric Connectivity The corpus callosum is a band of neural fibers that connects the right and left hemispheres of the brain. The results of some studies suggest that there are sex differences in the size of the corpus callosum: The posterior portion of the corpus callosum is larger in females than males.

21 Corpus Callosum

22 On the basis of this difference, some researchers have argued that the brain hemispheres communicate more effectively among females than males. Notably, however, some studies (e.g., Clark et al., 1993) have failed to demonstrate sex differences in the size of the corpus callosum.

23  Other Neuroanatomical Differences The brains of males are slightly larger than the brains of females. However, neurons are more densely packed in the brains of females than in the brains of males. Right vs. left hemisphere weight differences are smaller for females than for males.

24 Activity of the left amygdala is associated with long-term memory of emotional events in females; activity of the right amygdala is associated with long-term memory of emotional events in males (Cahill et al., 2004). Activity of the left hippocampus is associated with memory of object location in females; activity of the right hippocampus is associated with memory of object location in males (Frings et al., 2006).

25 The sexually dimorphic nucleus is 2.5 times larger in adult males than adult females. Although its function is unknown, the area in which it is located (the anterior hypothalamic preoptic area) is associated with sexual and parental behaviour, gender identity, and the regulation of gonadal hormones (Breathnach, 1990).

26 1. What biological theories have been proposed to explain gender differences? (continued) Biological Explanations of Gender Differences: