10. Reproductive Behaviors

Question 1

At an early stage of embryological development, before the influence of sex hormones, what is the appearance of a fetus’s external genitals?

a. A male has a small penis and a female has a small clitoris.
b. Both sexes have both a penis and a clitoris.
c. Both sexes have small “unisex” structures that could develop into either a penis or a clitoris.
d. Neither sex has any external genitals.

Answer 1

c.Both sexes have small “unisex” structures that could develop into either a penis or a clitoris

Question 2

Sex hormones affect neurons in several ways. Which of the following is not one of those ways?

a. They bind to membrane receptors.
b. They activate certain proteins in the cell’s cytoplasm.
c. They attach to chromosomes and activate or inactivate genes.
d. Brain enzymes convert them into dopamine and other neurotransmitters.

Answer 2

d.Brain enzymes convert them into dopamine and other neurotransmitters.

Question 3

What is the main difference between organizing effects and activating effects of hormones?

a. Organizing effects are long-lasting, whereas activating effects are temporary.
b. Organizing effects alter brain activity, whereas activating effects alter other parts of the body.
c. Organizing effects are excitatory, whereas activating effects are inhibitory.
d. Organizing effects depend on estrogens, whereas activating effects depend on androgens.

Answer 3

a.Organizing effects are long-lasting, whereas activating effects are temporary.

Question 4

If a developing mammal is exposed to high levels of both androgens and estrogens, its external anatomy will appear ______. If it is exposed to low levels of both, its external anatomy will appear ______.

a. masculine . . . feminine
b. feminine . . . masculine
c. masculine . . . intermediate
d. intermediate . . . feminine

Answer 4

a.masculine . . . feminine

Question 5

How does sexual differentiation of the brain differ between rodents and primates?

a. In rodents it depends on the level of testosterone. In primates it depends on the level of estradiol.
b. In rodents it depends on the level of estradiol. In primates it depends on the level of testosterone.
c. In rodents, testosterone must be aromatized to estradiol before it affects developing neurons.
d. In primates, testosterone must be aromatized to estradiol before it affects developing neurons.

Answer 5

c.In rodents, testosterone must be aromatized to estradiol before it affects developing neurons.

Question 6

How much a child plays with boys’ toys is apparently increased by prenatal exposure to ______ and decreased by prenatal exposure to ______.

a. cortisol . . . estradiol
b. testosterone . . . phthalates
c. high temperatures . . . low temperatures
d. cocaine . . . alcohol

Answer 6

b.testosterone . . . phthalates

Question 7

In terms of neurotransmitter activity, how does the mechanism of erection differ from that of orgasm?

a. Erection depends on acetylcholine, and orgasm depends on serotonin.
b. Erection depends on increased dopamine release, and orgasm depends on decreased dopamine release.
c. Erection depends on one set of dopamine receptors, and orgasm depends on different dopamine receptors.
d. Erection depends on serotonin, and orgasm depends on nitric oxide.

Answer 7

c.Erection depends on one set of dopamine receptors, and orgasm depends on different dopamine receptors.

Question 8

Compared to other men, what are the testosterone levels of married men?

a. Lower than average
b. About the same as average
c. Higher than average

Answer 8

a.Lower than average

Question 9

At what time, if any, during the menstrual cycle do women’s sexual desires tend to be highest, in women not taking birth-control pills?

a. On average, sexual desire does not change over the cycle.
b. Sexual desire is highest just after the menstrual period.
c. Sexual desire is highest during the periovulatory period.
d. Sexual desire is highest about a week after the periovulatory period.

Answer 9

c.Sexual desire is highest during the periovulatory period.

Question 10

What effect, if any, do sex hormones have on people’s ability to recognize facial expressions of emotion?

a. Estradiol impairs the ability to recognize emotional expressions.
b. Testosterone improves the ability to recognize emotional expressions.
c. Testosterone impairs the ability to recognize emotional expressions.
d. No evidence suggests any effect of sex hormones on the ability to recognize emotional expressions.

Answer 10

c.Testosterone impairs the ability to recognize emotional expressions.

Question 11

What hormonal levels, if any, correlate with the amount of time and care that human fathers give their young children?

a. High levels of prolactin and low levels of testosterone
b. High levels of both testosterone and estradiol
c. Low levels of both estradiol and prolactin
d. Fathers’ behavior does not correlate significantly with anything about hormones.

Answer 11

a.High levels of prolactin and low levels of testosterone

Question 12

What is meant by  “sexual selection”?

a. Having an XX or XY chromosome pattern determines whether one develops as a female or a male.
b. Hormones during a sensitive period produce long-lasting effects on anatomy and behavior.
c. Some people choose to switch from one gender identity to another.
d. Evolution favors characteristics that make an individual more appealing to the opposite sex.

Answer 12

d.Evolution favors characteristics that make an individual more appealing to the opposite sex.

Question 13

In a fetus with congenital adrenal hypertrophy (CAH), the adrenal gland produces ___ cortisol, and as a result, the pituitary directs the adrenal gland to produce ___ testosterone.

a. less than average . . . less than average
b. less than average . . . more than average
c. more than average . . . less than average
d. more than average . . . more than average

Answer 13

b.less than average . . . more than average

Question 14

A girl’s interest in boys’ toys correlates positively with which of the following?

a. The size of her hippocampus
b. Exposure to testosterone before birth
c. Exposure to cortisol before birth
d. Exposure to estradiol before birth

Answer 14

b.Exposure to testosterone before birth

Question 15

What condition occurs if a male lacks the receptor that enables androgens to activate genes in a cell’s nucleus?

a. Klinefelter’s syndrome
b. Congenital adrenal hyperplasia
c. Testicular feminization
d. Turner’s syndrome

Answer 15

c.Testicular feminization

Question 16

When genetic males lacked the enzyme that converts testosterone to dihydrotestosterone, what happened to their sexual development?

a. They developed an exaggerated male anatomy.
b. They looked female at birth but developed male structures at puberty.
c. They looked male at birth but developed female structures at puberty.
d. They developed as females, except without menstruation or pubic hair.

Answer 16

b.They looked female at birth but developed male structures at puberty.

Question 17

.On average, how do heterosexual and homosexual men compare in height?

a. On average, heterosexual men are several inches taller.
b. On average, heterosexual men are only very slightly taller.
c. On average, heterosexual and homosexual men are equal in height.
d. On average, homosexual men are taller.

Answer 17

b.On average, heterosexual men are only very slightly taller.

Question 18

Of the following, which is the least plausible hypothesis for why natural selection has not eliminated genes for male homosexuality?

a. Perhaps the relatives of a homosexual male have more than an average number of children.
b. Homosexual people might spread their genes by helping their brothers and sisters rear their children.
c. Maybe there is no gene for homosexuality. Instead, an environmental event produces an epigenetic effect that can be transmitted from one generation to the next.
d. Some homosexual men have children.

Answer 18

d.Some homosexual men have children.

Question 19

Which of the following would increase the probability that a boy will develop a homosexual orientation?

a. Living in a family with one or more older sisters
b. Living in a family with an older, adopted brother
c. Having a biological older brother, even if he did not live in the same house
d. Having either an adopted or biological younger brother

Answer 19

c.Having a biological older brother, even if he did not live in the same house

Question 20

.How might stress to a pregnant rat alter the sexual orientation of her male offspring?

a. Stress increases synthesis of the neurotransmitter acetylcholine.
b. Stress decreases synthesis of alpha-fetoprotein.
c. Stress increases the release of endorphins in the hypothalamus.
d. Stress decreases the release of corticosterone or cortisol from the adrenal glands.

Answer 20

c.Stress increases the release of endorphins in the hypothalamus.

Question 21

In what way was INAH-3 distinctive for most of the homosexual men in LeVay’s study and the follow-up research?

a. This nucleus had fewer than average neurons but only in men who died of AIDS.
b. This nucleus had fewer than average neurons regardless of the cause of death.
c. This nucleus had neurons with smaller than average volume.
d. This nucleus had fewer neurons, but each of them had a larger than average volume.

Answer 21

c.This nucleus had neurons with smaller than average volume.

Question 22

What does the SRY gene do?

Answer 22

The SRY gene (sex-determining region on the Y chromosome) causes the undifferentiated gonad of a mammal to develop into a testis, which then produces testosterone and MIH to direct development toward the male pattern.

Question 23

How do sex hormones affect neurons?

Answer 23

Sex hormones, which are steroids, bind to receptors on the membrane, activate certain proteins in the cell’s cytoplasm, and activate or inactivate particular genes

Question 24

What would be the genital appearance of a mammal exposed to high levels of both androgens and estrogens during early development? What if it were exposed to low levels of both?

Answer 24

A mammal exposed to high levels of both male and female hormones will appear male. One exposed to low levels of both will appear female. Genital development depends mostly on the presence or absence of androgens, and is nearly independent of estradiol levels.

Question 25

From the standpoint of protecting a male fetus’s sexual development, what are some drugs that a pregnant woman should avoid?

Answer 25

Pregnant women should avoid alcohol, marijuana, haloperidol, phthalates, and cocaine because these drugs interfere with male sexual development. Even aspirin and the chemicals lining bottles and cans produce mild abnormalities. Obviously, the results depend on both quantities and timing of exposure to these chemicals.

Question 26

How would the external genitals appear on a genetic female rat that lacked alpha-fetoprotein?

Answer 26

A female that lacked alpha-fetoprotein would be masculinized by her own estradiol, as researchers have in fact demonstrated (Bakker et al., 2006).

Question 27

What evidence most directly links children’s toy play to prenatal hormones?

Answer 27

Girls whose mothers had higher testosterone levels during pregnancy tend to play with boys’ toys more than the average for other girls. Boys whose mothers had higher phthalate exposure tend to play with boys’ toys less than the average for other boys.

Question 28

By what mechanism does testosterone affect the hypothalamic areas responsible for sexual behavior?

Answer 28

Testosterone primes hypothalamic cells to be ready to release dopamine. It also increases sensitivity in the genital area.

Question 29

Why do married men tend to have lower testosterone levels than single men of the same age?

Answer 29

Men with lower testosterone levels are more likely to get married than are men with higher testosterone levels. There may also be a tendency for testosterone levels to drop after marriage.

Question 30

At what time in a woman’s menstrual cycle do her estradiol levels increase? When are they lowest?

Answer 30

Estrogen levels increase during the days leading up to the middle of the menstrual cycle. They are lowest during and just after menstruation.

Question 31

When someone demonstrates an anatomical difference between male and female brains, on average, what if anything can we conclude about its role in behavior?

Answer 31

Until we have further evidence, we should not conclude anything. It is easy to speculate about how brain differences produce behavioral differences between men and women, but it is harder to test those speculations with solid data.

Question 32

What factors are responsible for maternal behavior shortly after rats give birth? What factors become more important in later days?

Answer 32

The early stage of rats’ maternal behavior depends on a surge in the release of the hormones prolactin and estradiol. A few days later, her experience with the young decreases the vomeronasal responses that would tend to make her reject them. Experience with the young maintains maternal behavior after the hormone levels begin to drop.

Question 33

What evolutionary advantage is suggested for why women are more interested in men’s wealth and success than men are interested in women’s wealth?

Answer 33

During pregnancy and early child care, a female is limited in her ability to get food and therefore prefers a male partner who can provide for her. A healthy male is not similarly dependent on a female.

Question 34

What is a common cause for a genetic female (XX) to develop a partly masculinized anatomy?

Answer 34

If a genetic female is genetically deficient in her ability to produce cortisol, the pituitary gland does not receive negative feedback signals and therefore continues stimulating the adrenal gland. The adrenal gland then produces large amounts of other hormones, including testosterone, which masculinizes development.

Question 35

If a genetic female is exposed to extra testosterone during prenatal development, what behavioral effect is likely?

Answer 35

A girl who is exposed to extra testosterone during prenatal development is more likely than most other girls to prefer boy-typical toys.

Question 36

What would cause a genetic male (XY) to develop a partly feminized external anatomy?

Answer 36

A genetic male with a gene that prevents testosterone from binding to its receptors will develop an appearance that partly or completely resembles a female.

Question 37

When children who had been reared as girls reached puberty and grew a penis and scrotum, what happened to their gender identity?

Answer 37

Most changed their gender identity from female to male.

Question 38

For which kind of twin pair is the concordance for sexual orientation greatest?

Answer 38

Monozygotic twins have higher concordance than dizygotic twins. Be sure to state this point correctly: Do not say that homosexuality is more common in monozygotic than dizygotic twins. It is the concordance that is greater—that is, the probability that both twins have the same sexual orientation.

Question 39

It seems difficult to explain how a gene could remain at a moderately high frequency in the population if most men with the gene do not reproduce. How would the hypothesis about epigenetics help with the explanation?

Answer 39

According to this hypothesis, some unidentified event in the environment can attach an acetyl group or a methyl group to some gene, increasing or decreasing its activity. That gene modification could be passed to the next generation, producing evidence for a hereditary effect, even though there is no “gene for homosexuality.” If events like this happen often enough, the result could be a moderately high prevalence of homosexuality, even if men with the inactivated gene seldom reproduce.

Question 40

By what route might having an older brother increase the probability of male homosexuality?

Answer 40

Having an older brother might increase the probability of male homosexuality by altering the mother’s immune system in the prenatal environment. The effect of the older brother does not depend on growing up in the same home.

Question 41

How might stress to a pregnant rat alter the sexual orientation of her male offspring?

Answer 41

Evidently, the stress increases the release of endorphins in the hypothalamus, and very high endorphin levels can block the effects of testosterone.

Question 42

In LeVay’s study, what evidence argues against the idea that INAH-3 volume depends on AIDS rather than sexual orientation?

Answer 42

The average size of INAH-3 was about the same for heterosexual men who died of AIDS and those who died of other causes. One homosexual man who died of other causes had about the same size INAH-3 as heterosexual men who died of AIDS.