Instructor’s Manual
by Amy Wisniewski
to accompany
Discovering Human Sexuality, Second Edition
Chapter 4 Sex and Gender Differences
Chapter Overview
Males and females differ anatomically, physiologically, and behaviorally. How humans
develop as male or female is explained at the beginning of the chapter. Disorders of sex
development—or conditions in which chromosomal, gonadal, or genital sex are
discordant or ambiguous—are also described.
Gender, or the mental and behavioral traits attributed to males or females, is considered
from both biological and social/environmental perspectives. Most likely, gender develops
as a result of complex interactions between biological and social influences. Finally,
transexual people possess the biology of one sex but the gender identity of the opposite
sex.
Chapter Outline
Genes and Hormones Guide Sex Development
Female and male reproductive tracts develop from different precursors
Female and male external genitalia develop from the same precursors
The gonads descend during development
Puberty is sexual maturation
The brain also differentiates sexually
Sex Development May Go Awry
Chromosomal anomalies affect growth and fertility
The gonads or genitals may be sexually ambiguous
Gender Is a Central Aspect of Personhood
Gender identity might not match anatomical sex
Box 4.1: Personal Points of View: My Life With Androgen Insensitivity Syndrome
Women and men differ in a variety of cognitive and personality traits
Differences in sexuality include attitudes toward casual sex, jealousy, and frequency
of masturbation
Many gender differences arise early in life
Biological Factors Influence Gender
Evolutionary forces act differently on females and males
Experiments demonstrate a role for sex hormones
Box 4.2: Biology of Sex: “Eggs at Twelve”
Life Experiences Influence Gender
Gender is molded by socialization
Box4.3: Personal Points of View: The Boy Who Was Raised as a Girl
Cognitive developmental models emphasize thought processes
Gender Development Is Interactive
Transgender People Cross Society’s Deepest Divide
Transexuals are of more than one kind
Box 4.4: Cultural Diversity: Transgenders in Cross-Cultural Perspective
Changing sex is a multistage process
Box 4.5: Controversies: How Should We Treat Gender-Dysphoric Children?
Some transgenders do not want surgery
Transgenders and transexuals struggle for awareness and acceptance
Chapter Summary
1. Sex is usually determined by the sex chromosomes: The XX pattern causes female
development, and the XY pattern causes male development. The key player in male
development is the gene SRY on the Y chromosome, which induces the embryo’s genital
ridges to become testicles. In the absence of SRY, the genital ridges become ovaries.
2. The male and female internal reproductive tracts develop from different precursors—
the Wolffian and Müllerian ducts. In XY embryos, the testicles secrete anti-Müllerian
hormone (AMH), which causes the Müllerian ducts to regress, and androgens, which
cause the Wolffian ducts to develop further and produce the male internal anatomy. In
XY embryos lacking functional androgen receptors (a condition called androgen
insensitivity syndrome), neither the male nor the female reproductive tract develops. In
XX embryos (normal females), the lack of AMH allows the Müllerian ducts to develop
further, and the lack of androgens allows the Wolffian duct to regress, producing the
female internal anatomy.
3. The external genitalia of the two sexes develop from common precursors. The urethral
folds give rise to the labia minora in females and to the shaft of the penis in males. The
genital swellings give rise to the labia majora in females and the scrotum in males. The
genital tubercle forms the external portion of the clitoris in females and the glans of the
penis in males. Male-typical development of the external genitalia requires the presence
of testosterone and its conversion to 5α-dihydrotestosterone (DHT). In female fetuses that
are exposed to high levels of androgens (as in congenital adrenal hyperplasia), the
external genitalia are partially masculinized.
4. Some sexual differentiation of the brain occurs prenatally— high levels of androgens
drive male-typical brain development, and low levels permit female-typical development.
At puberty and thereafter, estrogens become important in establishing and maintaining
female-typical body structure and function and also influence the brain.
5. Disorders of sex development include chromosomal anomalies such as Klinefelter
syndrome (XXY) and Turner syndrome (XO), as well as genetic conditions that affect
sex hormone production (e.g., congenital adrenal hyperplasia) or the body’s sensitivity to
sex hormones (e.g., androgen insensitivity syndrome). The proper treatment of children
with ambiguous genitalia is a subject of controversy.
6. Gender is the entire collection of mental traits that differ between women and men.
Gender identity is a person’s core sense of being a woman or a man. Gender role is the
social expression of gender identity.
7. Women outperform men in fine movements, verbal fluency, and some aspects of
memory. Men outperform women in some cognitive traits, such as visuospatial skills.
Personality differences include greater aggressiveness in men. In the area of sexuality,
men and women differ in frequency of masturbation (men masturbate more frequently),
attitudes toward casual sex (men are more approving), and styles of jealousy (women are
more likely to experience emotional jealousy; men are more likely to experience sexual
jealousy). All these gender differences show considerable overlap between the sexes, and
their significance is debated.
8. Many gender differences arise early in life. Most children distinguish perceptually
between males and females by 1 year of age, can identify their own sex by 2 to 3 years,
and understand the immutability of sex by 3 to 4 years. Males are more active than
females. Boys are more aggressive than girls. Boys and girls prefer different toys, and
both prefer to associate with children of their same sex. Sexspecific interaction styles
develop within these same-sex groups. Differences in other cognitive traits emerge
gradually during childhood.
9. Biological factors influence gender. These include genes that have evolved to help men
and women improve their reproductive success. A role for sex hormones, especially
during prenatal life, is illustrated by experiments on animals, by observation of humans
affected by endrocrinological disorders, and by the study of anatomical markers (such as
finger-length ratios) that are correlated with gender traits.
10. Socialization influences gender. This can happen through the innumerable rewards
and punishments that children receive from parents and others. Imitation is also an
important mediator of gender learning.
11. A variety of cognitive developmental models stress the importance of children’s
thought processes in the development of gender. The understanding of gender develops
sequentially in young children. Gender schemas are frameworks of beliefs that influence
perception and that tend to encourage either/or thinking about gender. In sexual script
theory, gender learning involves the social negotiation of roles, such as those to be played
by the man and woman in heterosexual relationships.
12. Transgender people are those whose gender identity does not match their biological
sex. Transexuals are transgender people who seek to change their anatomical sex: They
may transition from male to female (M-to-F) or from female to male (F-to-M).
13. All F-to-M transexuals and some M-to-F transexuals have a childhood history of
strong gender nonconformity. They dislike the bodily changes induced by puberty and
may attempt to conceal them. They are usually homosexual in the sense that they are
sexually attracted to persons of the same birth sex as themselves. They usually do not
identify as gay, however, but rather as heterosexual individuals. Some heterosexual M-toF transexuals have a different developmental history, in which the desire to change sex
develops out of a wish to incorporate their sexual targets (women) into their own bodies
(autogynephilia).
14. Sex reassignment is a multistage process involving living for some period in the
identity of the other sex, followed by hormonal treatments and, sometimes, sexreassignment surgery. Genitals can be transformed into those of the other sex, but the
procedure is expensive and, particularly in the case of F-to-M reassignment, yields
imperfect results. Nevertheless, many transexuals are satisfied with the results of sex
reassignment and are able to surmount the social and sexual challenges of post-transition
life.
15. Other transgender people do not seek sex reassignment for a variety of reasons. Some
believe that sex reassignment would be unnecessary if society could be persuaded to
loosen its rigid ideas about gender. All transgender people face discrimination and the
risk of violence, and most states and the federal government fail to offer them specific
protections.
Lecture Notes
(Bulleted items are grouped as suggested slides for presentation purposes.)
Genes and Hormones Guide Sex Development (Figure 4.1)
 Testes and ovaries form from the precursor gonads
 The gene that instructs the ridges to differentiate into testes is called SRY
o This gene is located on the Y chromosome
Male and Female Reproductive Tracts Develop from Different Precursors (Figure
4.2)
 Embryos of both sexes possess both Wolffian and Müllerian ducts
o Wolffian ducts are precursors of the male reproductive tract
o 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.
Male and Female External Genitalia Develop from the Same Precursors (Figure 4.3)
 Female and male external genitalia have the same developmental origin.
 The testicles descend during development (Figure 4.4)

Most prenatal sex development occurs during weeks 8 through 24 of gestation,
when testosterone levels are high in male fetuses
The Brain Also Differentiates Sexually
 There are differences in brain structure, function, and chemistry between the two
sexes
o These differences are brought about by higher levels of androgens in males
than in females during development
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
o Klinefelter syndrome (XXY, XXXY)
o Turner syndrome (XO)
o XYY syndrome
o Triple-X syndrome
 The gonads or genitals may be sexually ambiguous
o Gonadal intersexuality
o Androgen Insensitivity Syndrome (AIS) (Box 4.1)
o Congenital adrenal hyperplasia (CAH) (Figure 4.6)
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 (Figures 4.7, 4.8A, and 4.8B)
 Differences in sexuality include attitudes toward casual sex, jealousy, and
frequency of masturbation

Many gender differences arise at a young age.
o By about 3 years of age, most children show evidence of gender constancy
(Figure 4.9)
o By about 1 year of age, most children can distinguish between men and
women
o Differences in toy preferences (Figure 4.10)
Biological Factors Influence Gender
 Evolutionary factors influence gender development (Figures 4.11).
o 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
Experiments Demonstrate a Role for Sex Hormones



Girls with CAH have behavioral traits shifted in the masculine direction (Figure
4.12)
Prenatal androgens influence gender (Box 4.2 and Box 4.3)
The 2D:4D ratio correlates with many gendered characteristics (Figure 4.13)
Life Experiences Influence Gender
 Life experiences influence gender development beginning early in life (Figure
4.14)
o Observing socialization (Figure 4.15 A and B)
o Rewards and punishments
o Imitation (Figure 4.16)
 Cognitive models focus on thought processes.
o Gender schemas (Figure 4.17)
o Sexual scripts
Transgendered People Cross Society’s Deepest Divide
 Unhappiness caused by discordance between anatomical sex and gender identity
is called gender dysphoria
o F-to-M transexuals (trans men)
o M-to-F transexuals (trans women)
▪ Transvestism
▪ Autogynephilia
o Sex-reassignment is a multistage process (Figure 4.19)
o Some transexuals do not desire surgery (Figures 4.20 and 4.21)
o Some medical centers treat pre-pubertal children affected by gender dysphoria
(Box 4.5)
o Transgenders and transexuals struggle for awareness and acceptance (Figure
4.22)
Class Discussion Questions
1. People with DSD are sometimes depicted as having both male and female external
genitalia. Is this biologically possible?
2. Women and men differ in their performance on some cognitive tasks. Do you think
that learning or socialization contributes to these differences? Why or why not?
3. Gender development probably involves complex interactions between biology and
socialization. Did both types of influences affect the development of David Reimer (Box
4.3)? Why or why not?
4. Would you consider a F-to-M transexual who is attracted to women heterosexual,
homosexual, or neither? Why?
5. If a M-to-F transexual did not wish to have genital surgery, would you question their
gender dysphoria? Why or why not?
Teaching Suggestions/Resources
1. Eugenides, Jeffrey. (2003). Middlesex: A Novel. New York: Macmillan.
2. Bailey, J.M. (2003). The man who would be queen: The science of gender-bending and
transsexualism. Joseph Henry Press.
3. Fine C. (2010). Delusions of gender: How our minds, society, and neurosexism create
difference. W.W. Norton & Company, NY.