This is the 2007 version. Click here for the 2017 chapter 16 table of contents.

Summary: Sexual Behavior

Sexual development begins with the sexual differentiation of the fetus in the womb. If no male hormones are present, the fetus will develop as a female, even if it has the male XY genetic pattern. The events of early sexual development proceed in a series of stages that produce abnormalities if disrupted. After a baby is born, it has no gender-specific behavioral characteristics. Experiments show people take their cues from a baby's hair and clothes. If a boy baby is dressed as a girl (or vice versa) it elicits the sort of behavior generally reserved for the other gender.

Puberty is accompanied by development of secondary sex characteristics such as a deepening voice (in males), breast development (in females) and development of pubic hair (in both sexes). Menstruation may be delayed in girls who are very thin or who exercise extremely vigorously over a long period, such as ballerinas.

Adult sexual arousal was not systematically studied until the work of Masters and Johnson. They fitted volunteers, some of whom were prostitutes, with measuring devices. They defined a four-stage model of sexual arousal. Some researchers complain this model was prematurely enshrined and not all the four stages are distinct. Other researchers added elements Masters and Johnson left out, such as desire. Sexual arousal is influenced by hormones. Hormones can be influenced by classical conditioning, so particular stimuli may become associated with sex. There is no evidence for sexual attractants or pheromones affecting humans. Novelty increases arousal in both non-humans and humans.

Deep kissing is common before sex among married couples. Affectionate mouth-play is common in all human cultures and may have evolved out of the universal greeting display of mammals. Alcohol lessens sexual inhibitions, but can reduce a male's ability to have sex. An attempt to study the effect of marijuana on sexual arousal was halted after negative publicity.

Studies of adult sexual response show that male and female orgasms are very similar. Sexual behavior in marriage typically declines after initial years of a marriage, but there are exceptions. An active sex life in middle age typically continues into old age.

Most psychologists no longer consider homosexuality a psychological abnormality. Signs of homosexuality are present in many individuals from early life, and there is no evidence it is caused by parenting factors.

Historically, gay men and lesbians have shown somewhat different patterns of behavior. Before the AIDS epidemic, gay men tended to have many partners while lesbians were more likely to form lasting attachments. After AIDS more gay men pursudc monogamous relationships.

Saghir and Robins found in the 1970s that about two-thirds of gay men were called sissies as children, and about two-thirds of lesbians had a repetitive childhood wish to be a boy. Adult lesbians tend to emphasize emotional attachment rather than sex. Lesbians are also more likely to regard their sexual orientation as voluntary. As of the early 1980s only about 1 of 5 lesbians regarded their sexual orientation as a biological inevitability, while gay men were much more likely to feel their sexual orientation was natural and inevitable.

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