The Sexual Response Cycle
The headlines created by Kinsey’s 1940s survey reappeared after some 1960s studies in which scientists recorded the physiological responses of volunteers who masturbated or had intercourse. With the help of 382 female and 312 male volunteers – a somewhat atypical sample, consisting only of people able and willing to display arousal and orgasm while being observed in a laboratory – gynecologist-obstetrician William Masters and his collaborator Virginia Johnson (1966) monitored or filmed more than 10,000 sexual “cycles.”
Their description of sexual response cycle identified four stages, similar in men and women. During the initial excitement phase, the genital areas become engorged with blood, causing the man’s penis to become partially erect and woman’s clitoris to swell and the inner lips covering her vagina to open up. Her vagina also expands and secretes lubricant, and her breasts and nipples may enlarge.
In the plateau phase, excitement peaks as breathing, pulse, and blood pressure rates continue to increase. The penis becomes fully engorged and some fluid – frequently containing enough live sperm to enable conception – may appear at the tip of the penis. Vaginal secretion continues to increase, the clitoris retracts, and orgasm feels imminent.
Masters and Johnson observed muscle contractions all over the body during orgasm; these were accompanied by further increases in breathing, pulse, and blood pressure rates. A woman’s arousal and orgasm facilitate conception by helping propel semen from the penis, positioning the uterus to receive sperm, and drawing the sperm farther inward. A woman’s orgasm therefore not only reinforces intercourse, which is essential to natural reproduction, it also increases retention of deposited sperm (Furlow and Thornhill, 1996). In the excitement of the moment, men and women are hardly aware of all this but are more aware of their rhythmic genital contractions that create a pleasurable feeling of sexual release. The feeling apparently is much the same for both sexes. In one study, a panel of experts could not reliably distinguish between descriptions of orgasm written by men and those written by women (Vance & Wagner, 1976).
After orgasm, the body gradually returns to its unaroused state as the engorged genital blood vessels release their accumulated blood – relatively quickly if orgasm has occurred, relatively slowly otherwise. (It’s like the nasal tickle that goes away rapidly if you have sneezed, slowly otherwise.) During this resolution phase, the male enters a refractory period, lasting from a few minutes to a day or more, during which he is incapable of another orgasm. The female’s refractory period is not very long, which may make it possible for her to have another orgasm if restimulated during or soon after resolution.
Psychology: Sixth Edition by David G Myers (pp 436-437)