Unlike hunger, sexual drive does not motivate people to fulfill a basic biological need. A lack of food leads to death; a lack of sex, on the other hand, does not. Both biological and psychological factors strongly influence sexual drive.
One of the first researchers to give a modern account of human sexuality wasAlfred Kinsey. In the 1940s, he and his colleagues interviewed more than 18,000 U.S. men and women about their sexual behavior and attitudes. In his comprehensive reports about human sexuality, Kinsey denounced the repressive social attitudes of his time, which he said bore little relation to actual sexual practices. Kinsey provided statistics showing that sexual practices varied widely and that even in the 1940s there was a high prevalence of masturbation and premarital sex. These statistics shocked many people of his day.
Critics of Kinsey’s research maintained three arguments:
Other pioneers of sexual research were William Masters and Virginia Johnson. In the 1960s, they studied several hundred male and female volunteers who agreed to either masturbate or have intercourse in a laboratory. Masters and Johnson hooked up the volunteers to instruments that measured various physiological indicators during sexual activity. Using the results of these studies, they described the sexual response cycle.
Masters and Johnson divided the human sexual response cycle into four phases:
Critics of Masters and Johnson’s research maintained two arguments:
Hormones alone cannot cause sexual arousal. Psychological factors are also highly influential.
A culture’s social and economic structure determines the gender roles that men and women adopt. These gender roles in turn determine people’s attitude toward sexual activity. In some cultures, for instance, women need marriage to get access to status and wealth. In such cultures, a woman is less likely to be interested in sex for its own sake, since casual sex can damage her reputation and reduce her chances of marriage.
Many researchers have found that some differences exist between men and women in sexual behavior and partner choice, though all men and all women do not behave the same way or feel the same things.
|More interested in sex; initiate and think about sex more often||Less interested in sex|
|Want sex with more partners||Not as interested in sex with many partners|
|Desire sex without emotional commitment||Desire sex with emotional commitment|
|Focus on youth and physical attractiveness when choosing a sex partner||Focus on social and economic status when choosing a sex partner|
|Feel more jealous when partner is physically unfaithful||Feel more jealous when partner is emotionally unfaithful|
Some theorists use evolutionary theory to explain these gender differences. Their explanations are generally based on Robert Trivers’s idea that men and women make different parental investments in order to produce offspring. From a biological standpoint, men invest no more than the energy required for intercourse. Women, on the other hand, invest time and energy in pregnancy and breast feeding. Because of these biological differences, females can produce only a limited number of offspring, whereas males can potentially produce virtually unlimited offspring.
Males can increase their reproductive success by producing as many offspring as possible. Evolutionary theory predicts that men tend to choose attractive, youthful partners because these qualities imply good health and an ability to reproduce successfully. Females increase their reproductive success by being highly discriminating when choosing mates. They try to select males who have the most access to material resources, because such males can contribute the most to caring for offspring.
Furthermore, men must contend with paternity uncertainty—they can never be certain that they are the fathers of their partners’ offspring. Evolutionary theorists predict that men would therefore tend to have concerns about their partners’ sexual infidelity. Women, on the other hand, can be certain that their offspring are their own, though they cannot be certain that their partners will provide for their offspring. Therefore, they are more likely to be concerned about the emotional fidelity of their partners.
Many people criticize the use of evolutionary explanations of gender differences in sexual behavior. Some critics argue that alternative explanations can account equally well for the observed gender differences. For example, women’s history of social and economic subservience may have taught them to place a high value on their partners’ access to material resources. Men’s preferences and behaviors may likewise be a product of socialization. See page 43 for more information on problems with evolutionary explanations.
Sexual orientation is such a controversial subject that people cannot even agree about how the term sexual orientation should be defined. Some people argue over whether it refers to sexual behavior, sexual attraction, emotional attraction, or all three.
Researchers define sexual orientation in a variety of ways, which means there is no clear idea about what proportion of the population is homosexual. Researchers also have many different opinions regarding how much biological and environmental factors contribute to sexual orientation.
Researchers have many ideas about the possible biological factors of homosexuality:
Many researchers believe biological factors alone can’t explain the origin of homosexuality. For example, there is only about a 50 percent chance that the identical twins of homosexual men will also be homosexual. Therefore, some other factor must make the other 50 percent heterosexual. Although this other factor remains unknown, researchers have proposed a number of environmental situations that might influence sexual orientation:
Many of these proposals lack empirical support.
At this time, no one knows exactly what determines sexual orientation. Possibly, men and women develop homosexual orientations through various pathways. It is also possible that the cause of homosexual orientation differs from individual to individual.