[Page 3097]Sexual desire was first introduced as a distinct phase of the human sexual response by Helen Singer Kaplan, who added it to William Masters and Virginia Johnson’s original four-stage model of sexual response, consisting of (1) arousal/excitation, (2) plateau (maintenance of elevated arousal), (3) orgasm, and (4) resolution (de-escalation of arousal). Kaplan asserted that a motivational stage necessarily preceded these, and thus in 1977, she proposed a triphasic model of sexual response, which begins with desire, progresses into arousal, and culminates in orgasm. Kaplan’s inclusion of desire in the sexual response made several assumptions about desire that laid the framework for how the construct came to be defined clinically for many years.

Kaplan’s model assumed a linear sequence initiating with a primarily spontaneous and biological ...