1. Sex and Gender Differences

2. Genes and Hormones Guide Sex Development
Testes and ovaries form from the precursor gonads The gene that instructs the ridges to differentiate into testes is called SRY This gene is located on the Y chromosome

3. Figure 4.1 Human chromosomes
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4. Male and Female Reproductive Tracts Develop from Different Precursors
Embryos of both sexes possess both Wolffian and Müllerian ducts
Wolffian ducts are precursors of the male reproductive tract
Müllerian ducts are precursors of the female reproductive tract
In males, testes produce anti-Müllerian hormone (AMH) to eliminate the female ducts
In females, the absence of AMH allows Müllerian ducts to persist and to develop into the oviducts, uterus, and deeper parts of the vagina

5. Figure 4.2 Development of the male and female reproductive tracts
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6. Male and Female External Genitalia Develop from the Same Precursors
Female and male external genitalia have the same developmental origin Most prenatal sex development occurs during weeks 8 through 24 of gestation, when testosterone levels are high in male fetuses The testicles descend during development

7. Figure 4.3 Development of the male and female external genitalia (Part 1)
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8. Figure 4.3 Development of the male and female external genitalia (Part 2)
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9. Figure 4.3 Development of the male and female external genitalia (Part 3)
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10. Figure 4.4 Descent of the testicles (Part 1)
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11. Figure 4.4 Descent of the testicles (Part 2)
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12. The Brain Also Differentiates Sexually
There are differences in brain structure, function, and chemistry between the two sexes
These differences are brought about by higher levels of androgens in males than in females during development

13. Sex Development May Go Awry
Chromosomal anomalies that do not fall under typical female (46,XX) or male (46,XY) chromosomal complements affect growth and fertility
Klinefelter syndrome (XXY, XXXY)
Turner syndrome (XO)
XYY syndrome
Triple-X syndrome
The gonads or genitals may be sexually ambiguous
Gonadal intersexuality
Congenital adrenal hyperplasia (CAH)
Androgen Insensitivity Syndrome (AIS)

14. Figure 4.6 Partial masculinization of genitalia in a girl with congenital adrenal hyperplasia
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15. Box 4.1 Personal Points of View: My Life With Androgen Insensitivity Syndrome
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16. Gender Is a Central Aspect of Personhood
Gender identity is the sense of which sex one belongs to. For some people, gender identity does not match anatomical sex This identity is expressed via gender role behavior Sexual orientation, cognition, and personality traits differ between men and women Differences in sexuality include attitudes toward casual sex, jealousy, and frequency of masturbation

17. Figure 4.7 Mental rotation task
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18. Figure 4.8A Test of object location memory
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19. Figure 4.8B Test of object location memory
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20. Gender Is a Central Aspect of Personhood
Many gender differences arise at a young age
By about 3 years of age, most children show evidence of gender constancy
By about 1 year of age, most children can distinguish between men and women
Differences in toy preferences

21. Figure 4.9 Gender constancy
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22. Figure 4.10 Toy preference test
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23. Biological Factors Influence Gender
Evolutionary factors influence gender development
Evolutionary factors:
Cognitive differences between the sexes due to long-standing division of labor between men and women
Difference in interest in casual sex between men and women
Jealousy

24. Figure 4.11 Monkeys show humanlike toy preferences
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25. Experiments Demonstrate a Role for Sex Hormones
Girls with CAH have behavioral traits shifted in the masculine direction Prenatal androgens influence gender The 2D:4D ratio correlates with many gendered characteristics

26. Box 4.2 Biology of Sex: “Eggs at Twelve”
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27. Box 4.3 Personal Points of View: The Boy Who Was Raised as a Girl
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28. Figure 4.12 Hormones and play
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29. Figure 4.13 Finger-length ratio and gender
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30. Life Experiences Influence Gender
Life experiences influence gender development beginning early in life
Observing socialization
Rewards and punishments
Imitation
Cognitive models focus on thought processes
Gender schemas
Sexual scripts

31. Figure 4.14 Babies enter a gendered world
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32. Figure 4.15 Influence of siblings on gender
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33. Figure 4.16 The media influence gender
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34. Figure 4.17 Influence of gender stereotypes on children’s memories
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35. Transgendered People Cross Society’s Deepest Divide
Unhappiness caused by discordance between anatomical sex and gender identity is called gender dysphoria
F-to-M transexuals (trans men)
M-to-F transexuals (trans women)
Transvestism
Autogynephilia

36. Transgendered People Cross Society’s Deepest Divide
Sex-reassignment is a multistage process
Some transexuals do not desire surgery
Some medical centers treat pre-pubertal children affected by gender dysphoria
Transgenders and transexuals struggle for awareness and acceptance

37. Figure 4.19 Chastity Bono transitioned to Chaz Bono in 2009
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38. Figure 4.20 The vulva after sex-reassignment surgery
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39. Figure 4.21 Transformation of the clitoris into a small penis
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40. Box 4.5 Controversies: How Should We Treat Gender-Dysphoric Children?
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41. Figure Kate Bornstein
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