Sexual attraction to members of the opposite sex is called heterosexuality.

The sex drive, or sexual desire, is an unlearned, powerful drive that human beings share with other animal species. Heterosexuals experience sexual desire for members of the opposite sex. This drive contrasts with those of homosexuals, where the object of sexual desire is a member of one's own sex.

Most researchers believe that children begin to notice physical differences between males and females by age two. As children grow, they learn about sex roles, gender identities, and sex differences through observation and through play. Children constantly observe their parents and other adults, including teachers and childcare providers, as well as the attitudes and behavior of their peers. Gender identity becomes established when a young boy both understands that he is a boy and thinks of himself as a boy. Gender identity becomes established when a young girl both understands that she is a girl and thinks of herself as a girl.

Although much research into underlying causes of sexual orientation has been done, little conclusive evidence has emerged about why one individual is heterosexual and another homosexual. Researchers have studied biological and genetic determinants, hormone levels, and environmental factors. Research shows that environmental and biological factors combine in the complex process of human development to establish sexual orientation. By adolescence, teenagers usually sense their dominant sexual preference. Although many people are curious about bisexual urges and fantasies, most people evolve into a preferred sexual orientation, heterosexual or homosexual, as they mature.

See also Bisexuality ; Sexual identity .



Beasley, Chris, et al. Heterosexuality in Theory and Practice. New York: Routledge, 2012.

Blank, Hanne. Straight: The Surprisingly Short History of Heterosexuality. Boston: Beacon Press, 2012.

Fisher, Seymour. Sexual Images of the Self: The Psychology of Erotic Sensations and Illusions. Hillsdale, NJ: Lawrence Erlbaum, 1989.

Johnson, Paul. Love, Heterosexuality, and Society. London: Routledge, 2012.


American Psychological Association. “Heterosexuality/ homosexuality: Dichotomy or Continuum.” http://www.apa.org/pubs/journals/special/2143101.aspx (accessed September 19, 2015).

National Institutes of Health. “Sexual Orientation and Human Development.” http://www.ncbi.nlm.nih.gov/pubmed/3689108 (accessed September 19, 2015).

PBS. “The Invention of Heterosexuality.” http://www.pbs.org/wgbh/pages/frontline/shows/assault/context/katzhistory.html (accessed September 19, 2015).