Unlike hunger, sexual drive does not motivate people to fulfill a basic biological need. A lack of food leads to death; a lack of sex, on the other hand, does not. Both biological and psychological factors strongly influence sexual drive.

Kinsey’s Studies

One of the first researchers to give a modern account of human sexuality wasAlfred Kinsey. In the 1940s, he and his colleagues interviewed more than 18,000 U.S. men and women about their sexual behavior and attitudes. In his comprehensive reports about human sexuality, Kinsey denounced the repressive social attitudes of his time, which he said bore little relation to actual sexual practices. Kinsey provided statistics showing that sexual practices varied widely and that even in the 1940s there was a high prevalence of masturbation and premarital sex. These statistics shocked many people of his day.

Critics of Kinsey’s research maintained three arguments:

  • Kinsey’s sample was not random. Instead, it consisted largely of well-educated, white city dwellers.
  • Kinsey and his colleagues used questionable methods to gather their data, especially asking leading questions when interviewing subjects.
  • Kinsey may have let his own beliefs influence his results.

Masters and Johnson’s Studies

Other pioneers of sexual research were William Masters and Virginia Johnson. In the 1960s, they studied several hundred male and female volunteers who agreed to either masturbate or have intercourse in a laboratory. Masters and Johnson hooked up the volunteers to instruments that measured various physiological indicators during sexual activity. Using the results of these studies, they described the sexual response cycle.

The Sexual Response Cycle

Masters and Johnson divided the human sexual response cycle into four phases:

  1. Excitement phase: Physiological arousal increases quickly. Muscle tension, heart rate, blood pressure, and breathing rate increase. In men, the penis gets erect and the testes swell. In women, the clitoris hardens and swells, the vaginal lips open, and the vagina lubricates.
  2. Plateau phase: Physiological arousal continues. In women, the clitoris retracts under the clitoral hood. Men may secrete a small amount of fluid from the penis.
  3. Orgasm phase: Physiological arousal peaks. Men ejaculate seminal fluid. Both men and women experience muscular contractions in the pelvic area, along with a sensation of pleasure.
  4. Resolution phase: Physiological responses return to normal levels. Men then go through a refractory period that can vary in length, during which they are not responsive to stimulation. The refractory period tends to get longer as men age.

Critics of Masters and Johnson’s research maintained two arguments:

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