A capacity for sexual response is present from infancy. According to contemporary data, about 40 percent of U.S. children have masturbated by the time they reach puberty. Recent studies indicate that children begin masturbating at somewhat earlier ages now than a generation or so ago. Children also engage in some heterosexual play, as well as some same-gender activity.

During adolescence there is an increase in sexual activity. According to one theory, this activity is influenced by the interaction of biological factors (increasing testosterone level) and social and psychological factors (for example, sexually permissive attitudes). By age 15, nearly all boys have masturbated. Girls tend to begin masturbating somewhat later than boys, and fewer of them do masturbate. Attitudes toward masturbation are considerably more permissive now than they were a century ago. About 10 percent of adolescents have homosexual experiences to orgasm, with this figure being slightly higher for boys than for girls.

Today the majority of males and of females alike have premarital sex. This is a considerable increase over the incidence reported in the Kinsey studies, done 50 years ago. Adolescents today are considerably more likely to use a variety of sexual techniques, including mouth-genital sex. There is variation in the incidence of premarital intercourse among various racial and ethnic groups in the United States, and even greater variability from one country to another.

The predominant sexual standard today is one of "permissiveness with affection"; that is, sex is seen as acceptable outside marriage, provided there is an emotional commitment between the partners.

Following Erik Erikson's theory, experiences with sexuality can serve important functions in a person's psychological development. They may be important, for example, in the process of becoming independent of parents and in establishing a viable moral system.