MODULE 5

The Sex Drive

Another important (and endlessly interesting) primary drive is sex. This module deals with the mechanisms of the sex drive.

The beneficiaries of the various motivations differ. Motivations such as hunger or thirst benefit the individual organism. If a man does not eat, he will die of starvation. Other motivations, such as the sex motivation, benefit the species. If organisms had no drive to mate, there would be no offspring and the species would not survive.

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The sex motivation is a tendency for an organism of one sex to copulate with an organism of the opposite sex. The member of the opposite sex is the incentive, and the drive-reducing behavior is sexual intercourse. In other motivations, such as thirst, the strength of the drive is fairly constant throughout life. The sex drive, however, increases in strength from birth until puberty, the age at which the organism is fully developed sexually. Later in life, it usually declines.

The sex drive is partly under glandular control

The gradual development of the sex drive is controlled by the endocrine system. The glands most directly involved are the gonads, or sex glands, but the pituitary grand also has some influence. The development of male sexuality is brought about through the action of androgens, male sex hormones secreted by the testes. The female sex hormones, estrogens, are secreted by the ovaries.

In an experiment done by Beach (1951) it was found that when an organism is castrated before puberty, normal sexual behavior does not develop and the organism is incapable of reproducing. This is true of human beings as well as the lower animals.

The effects of castration after puberty are not the same in humans and lower animals. In rats, castration after puberty has the same effect as castration before puberty: the permanent elimination of all sexual behavior. In humans, however, castration after puberty usually has little effect on the sex drive. This suggests that in humans after puberty, the sex hormones have a lessened effect on sexuality, and learning plays a more important role.

Though the glandular influence on the human sex drive seems to decrease after maturity, Hoskins (1941) found that he could revive declining sexual behavior by injecting men with androgens and females with estrogens. So it seems that hormonal influences over the sex drive decrease after maturity but do not disappear altogether.

But there are obvious physiological factors that continue to influence sexual and social reactions. An interesting study in Nature Genetics conducted at the Yerkes Center in Atlanta, was discussed in the New Yorker magazine (Collins, 2000). Some mice lacking in the hormone oxytocin appeared not to remember female mice with whom they have had previous contact. Male mice that did manufacture oxytocin did not spend as much time sniffing the females upon later contact. If true for humans alos, perhaps that is why some males forget to call their female partners after initial meeting, the article half seriously suggested.

Sexual motivation has two aspects. The first of these is arousability. Arousability is the potential for sexual arousal. When sexuality has developed normally in a human being, certain physiological arousal responses are predictable. Among these are increased blood pressure and heart rate, reddening of the skin and engorgement of the genitals with blood. These responses are automatic and unlearned. They are controlled by physiological processes.

The second aspect of the sex motivation is the behavior involved in satisfying or reducing the drive. In higher animals (man and the primates) mating behavior is learned. Nissen's study (1953) demonstrates this. Ten chimpanzees, five males and five females, were raised together and separated at puberty. One year after puberty, when the sex drive was at its highest, the chimps were brought together. They were repeatedly paired so that each chimp had the chance to mate with each chimp of the opposite sex. Not one pairing resulted in sexual intercourse, though fragments of the mating behavior were observed. Nissen concluded that in primates mating behavior is the result of trial-and-error learning.

Although sexual behavior in primates is also learned, sex is still considered a primary drive

Unlike primates, lower animals such as rats perform sexual intercourse in a stereotyped way. The mating behavior always follows a specific pattern. In lower animals, the pattern of behavior during the sex act is probably innate.

Since the sex motive is based on physiological processes, the sex drive is a primary drive. Much human behavior that does not directly involve mating is, nevertheless, based on the sex drive. These behaviors involve secondary drives which are learned. They differ from culture to culture and from individual to individual. The most obvious secondary drives associated with sexual moti- vation involve courting behavior. Attending social functions such as musical concerts, meeting certain standards of dress, and writing love poems are motivated by secondary drives. The incentive of these secondary drives may be marriage, "going steady," or even a simple date, but these are all based on primary sexual motivation.

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MODULE 5 PROGRESS CHECK 1

Now test yourself without looking back.

1. The sex drive is necessary for survival of___________________________

2. Complete the following statements.

a. The male sex hormones are______________________

b. The female sex hormones are____________________________

3. The male hormones are secreted by the_______________________

4. The female hormones are secreted by the________________________

5. Which of the following is always under endocrine control?
a. The maintenance of sexual behavior in humans
b. The development of sexual behavior in both humans and lower animals
c. The maintenance of sexual behavior in lower animals

6. In lower animals such as rats, most sexual behavior is:
a. voluntary.
b. innate.
c. learned.
d. under strict neural control.

7. Name two physiological changes which take place during sexual arousal.
____________________________________
_____________________________________

8. Complete these statements.

a. Drives related to primary motivations are called________________________drives.

b. The drive which motivates an individual to engage in courting and marriage behavior is based on the_____________________________ drive.

ANSWER KEY

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MODULE 5
EXERCISES

Some motivations, such as hunger and thirst, are necessary for the survival of the individual. Others, such as those involving the sex and maternal drives, are not necessary for individual survival. The sex and maternal drives, however, are necessary for the survival of the________________________________________ _______________________________________ 3

The basic physiological mechanisms that are responsible for the sex drive involve the endocrine system. The sex drive is controlled mainly by:
a. electrochemical conduction.
b. the secretion of hormones.
c. the central nervous system.
d. activity of the circulatory system.
________________________________________ 7

Androgens, the male sex hormones, are secreted by which of the gonads?______________________________________________1

The ovaries secrete the female sex hormone called_______________________________6

Until puberty, sexual development in humans is incomplete. After puberty, however, humans are_____________________________ 4

In human beings and in animals the sex hormones are essential for the development of sexual behavior. What would be the likely effect on sexual behavior of castration before puberty?
a. Sexual behavior would be enhanced.
b. There would be no effect on sexual behavior.
c. The individual would die.
d. Sexual behavior would be severely disrupted.
____________________________________ 8

In male humans, when sexual behavior declines with age, sexual responses can be revived by:
a. injections of estrogens.
b. injections of thyroxin.
c. surgery.
d. injections of androgens.
e. (none of these)
___________________________________________2

The sex hormones are not essential for the maintenance of human sexual behavior. When adult males are castrated after puberty:
a. they no longer are capable of sexual behavior.
b. sexual behavior is not eliminated.
c. the sex drive is enhanced.
____________________________________ 5

ANSWERS

1 testes
2 d
3 species
4 fully developed sexually; sexually mature.
5 b
6 estrogen
7 b
8 d


Unlike humans, both the development and maintenance of sexual
behavior in lower animals are greatly dependent upon hommonal
secretions. When the ovaries of an adult female rat are removed:
a. the sex drive is enhanced.
b. sexual behavior is unchanged.
c. sexual behavior disappears.

__________________________________2
Unlike primates, the manner in which lower animals mate:
a. may differ from species to species but is always the same for all organisms in the same species.
b. is the same for all species.
c. varies in accordance with past experiences of the organisms involved.
d. differs from organism to organism within each lower species.

_______________________________5

There are two sides to human sexual behavior. Arousability (the capability of being aroused) is strongly dependent on hormones. The manner in which the drive is reduced, however, is based on past_______________________________________________1

Leaming and habit play a much greater role in human sexual behavior than in the sexual behavior of the lower animals. In fact, the reason that adult human sexual behavior is retained after eliminating sex hormones is because the sexual responses:
a. were previously inhibited by the endocrine system.
b. have been reamed and are no longer greatly dependent upon hormones.
c. are strengthened in later life.
d. are strengthened when not under the influence of the sex hormones.
________________________________________________4

Motivated behavior toward going steady is based on the sex drive.

The "going steady" drive is a____________________________motivation.
__________________________________________3

ANSWERS

1 learning or experience
2 c
3 secondary
4 b
5 a

NOW TAKE PROGRESS CHECK 2


MODULE 5
PROGRESS CHECK 2

1. Which of the following drives is most related to survival of the species?
a. Power
b. Social
c. Sex
d. Sleep

2. Complete the following statements.

a. Estrogen is the_____________________ sex hormone.

b. Androgen is the sex hormone.___________________________

3. The gonads secrete the ______________________hormones.

4. The effect of castration before puberty is:
a. the failure of development of sexual behavior.
b. a decrease in all bodily metabolism.
c. an enhancement of sexual behavior.
d. not the same for humans and lower animals.

5. In human sexual motivation, the form of the behavior involved in the satisfaction of the drive is:
a. innate.
b. learned.
c. controlled by sex hormones.
d. (none of these)

6. Genital engorgement and increased pulse pressure are examples of (learned/unlearned)_____________________________ human sexual responss.

ANSWER KEY

5 OR MORE CORRECT GO TO MODULE 6
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August 15, 2000