hormones, such as testosterone, and estrogen, as well as small amounts of testosterone, in
females. Secretion of hormones by the hypothalamus stimulates the pituitary gland to
secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH) into the blood-
stream, which stimulate gonads (testes in males and ovaries in females) to secrete testos-
terone and estrogen that initiate and maintain arousal. Without these two hormones, sexual
desire is greatly reduced in all species, but testosterone levels in humans seem related to
sexual motivation in both sexes. Humans seem less instinctively driven to have children
than other animals. Many learned cues are involved in this drive. Societies attempt to reg-
ulate sexual behavior by imposing sanctions against incest and encouraging or discouraging
masturbation, premarital intercourse, marital intercourse, extramarital intercourse, and
homosexuality.
In the 1940s, when biology professor Alfred Kinsey coordinated preparation for a mar-
riage course, he found little scientific information available about sex and decided to pursue
that research. He began to interview people about their sex histories, trained other inter-
viewers, and founded the Institute for Sex Research, now the Kinsey Institute, at Indiana
University. His popular book Sexual Behavior in the Human Malewas based on thousands
of interviews, although participants were not randomly selected. A similar book about
females followed.
Sexual orientation refers to the direction of an individual’s sexual interest.
Homosexualityis a tendency to direct sexual desire toward another person of the same sex,
and bisexuality is a tendency to direct sexual desire toward people of both sexes.
Heterosexualityis a tendency to direct sexual desire toward people of the opposite sex.
While most people are heterosexual, about 10% are estimated to be homosexual.
Researchers attribute the causes of homosexuality to biological, psychological, and sociocul-
tural factors.
Although the sex drive is not necessary for survival of an individual, it is necessary for
survival of the species. According to evolutionary psychologists, mammalian females lack
incentive to mate with many males because they optimize reproductive success by being
selective in mating, choosing a male who has resources to provide for children. On the other
hand, males optimize reproductive success by mating with many females, choosing young,
healthy, fertile females.
Masters and Johnson described a pattern of four stages in the biological sexual
response cycleof typical men and women, including excitement characterized by sexual
arousal; plateau, which involves increased breathing rate, muscle tension, heart rate, and
blood pressure; orgasm, which is characterized by ejaculation in males and pleasurable sen-
sations induced by rhythmic muscle contractions in both sexes; and resolution as blood
leaves the genitals and sexual arousal lessens, followed in most males by a refractory period
during which another erection or orgasm is not achieved. Females show less tendency for
a refractory period and are often capable of multiple orgasms.Social Motivation
Achievement
According to David McClelland, the achievement motive is a desire to meet some
internalized standard of excellence. McClelland used responses to the Thematic
Apperception Test (TAT)to measure achievement motivation. He suggested that people
with a high need for achievement choose moderately challenging tasks to satisfy their
need. They avoid easy goals that offer no sense of satisfaction and avoid impossible goals
that offer no hope of success. People low in need for achievement select very easy or
impossible goals so that they do not have to take any responsibility for failure. College stu-152 STEP 4. Review the Knowledge You Need to Score High
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