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The heterosexual–homosexual continuum or the sexual orientation continuum is a psychological and philosophical understanding of human sexuality that places sexual orientation on a continuous spectrum from heterosexuality to homosexuality, with sexuality ranging from exclusive attraction to the opposite sex to exclusive attraction to the same sex.
This concept stems from Alfred Kinsey's 1940s surveys of sexuality; significant numbers of Kinsey's subjects reported bisexuality of varying degrees, rather than the strict heterosexual/homosexual division that had been previously assumed. This work was expanded by Fritz Klein, who hypothesized that sexual orientation was a dynamic, multi-variable process, involving attraction, behavior, fantasies, emotional and social preferences, self-identification, and lifestyle. This continuum was an important influence on the feminist and gay-rights movements of the 1970s and 1980s as academics and movement leaders tried to distinguish between one's sex—e.g. being male or female—and the social, cultural, and psychological aspects of gender and sexuality.
According to a 2005 statement by the American Psychological Association:
Sexual orientation is an enduring emotional, romantic, sexual, or affectionate attraction toward others. It is easily distinguished from other components of sexuality including biological sex, gender identity (the psychological sense of being male or female), and the social gender role (adherence to cultural norms for feminine and masculine behavior).
People who disagree with this interpretation of human sexual orientation are said to believe in a "heterosexual–homosexual dichotomy".