Sexual Response Cycle

The four stages of human sexual response. Based on observations and interviews with people, Masters and Johnson (1966) identified the following four stages. The first stage is the excitement phase, during which physical arousal increases quickly. This arousal is indicated by increased muscle tension, breathing, and heart rate, as well as increase in blood pressure. Due to vasocongestion, the enlargement of blood vessels, the penis erects, and the clitoris becomes harder and swells, while the vagina becomes lubricated. During the second stage, the plateau phase, physiological arousal still increases but at a notably reduced rate. For example, in women, the vaginal entry becomes tighter. The majority of men may secrete a small drop of fluid at the top of the penis. This drop may hold a small amount of sperm but is not the same as ejaculate. Depending on the length of foreplay, the sexual arousal may vary and fluctuate in men and women. The third stage is the orgasm stage, during which arousal is at its highest point. Orgasm results in muscular contractions and spasms in the pelvic region and in a male, ejaculation of semen. Though women may be less likely than men to experience orgasm during intercourse, they are more likely to be multiorgasmic—that is, capable of having more than one orgasm. The final stage of the sexual response cycle is the resolution phase, during which levels of arousal return back to normal. After climax, men often experience a refractory period—that is, a time during which the male does not respond to stimulation. For more information, see Masters and Johnson (1966).