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Science Meets Sex: Understanding Sexual Response

Researchers have been studying sexual response for the past 40 years, and they have established that most people go through a predictable series of physical changes during sex. More recently, researchers have also examined the psychological components of sexual response, in order to help us understand what is happening to us emotionally during sexual activity.

Masters and Johnson

You may remember hearing about Masters and Johnson. In the early 1960s, William Masters, a gynecologist, and Virginia Johnson, a psychologist, worked together to study human sexual response. They were able to observe people having sexual intercourse in a laboratory and to identify the changes in the body, especially the genitals, that occur during heterosexual intercourse. Their first book, Human Sexual Response, published in 1966, sold millions of copies to a grateful public. In it, Masters and Johnson described a cycle of human sexual response that occurs in both men and women in four stages: excitement, plateau, orgasm, and resolution.

Excitement: During the excitement phase, as people become sexually aroused, increases are noted in heart rate, blood pressure, and muscular tension. In men, the testes begin moving closer to the body; the scrotal skin thickens; and the penis becomes erect. In women, the labia minora, the vagina, and the nipples increase in size; the clitoris becomes erect; and vaginal lubrication occurs.

Plateau: During the plateau phase, excitement becomes enhanced. The penis becomes fully erect and the testes move even closer to the body. The clitoris retracts under the clitoral hood; the inner two-thirds of the vagina expand; and the outer third engorges with blood. This stage often lasts only a few minutes, but by extending it, people report more intense sex and more intense orgasms.

Orgasm: In the Masters and Johnson model, orgasm follows the plateau phase if sexual activity continues. During orgasm, both men and women experience intense pelvic contractions at 0.8-second intervals (on average) and involuntary muscle spasms throughout the body.

In men, orgasm has two stages. During the emission stage, semen builds up in the urethra at the base of the penis. (This results from contractions in the prostate gland and the tubes that move semen from the testes to the penis.) The man feels a sense that nothing in the world could stop him from ejaculating--this is known as "ejaculatory inevitability." Next, during the expulsion stage, the muscles surrounding the urethra and the base of the penis contract, expelling semen from the urethra. For many men, the first few contractions are the most intense.

In women, the pelvic muscles and the uterus contract, usually between 3 and 15 times, each contraction lasting less than one second. The first 3 to 6 contractions are the most intense, followed by less intense and slower ones.

Interestingly, women do not have the same sensation of "inevitable" orgasm. In fact, most women report that even a minor disruption or change of clitoral stroking can cause them to lose their orgasm.

Resolution: During the resolution phase, the body returns to its pre-excitement state. Men experience a recovery period (also known as the refractory period) during which they can't have another orgasm. In young men, this may be a matter of minutes; in older men, it may be as much as a day or so, although some men do report multiple orgasms. Women may be able to have multiple orgasms or pass to the resolution phase without having had an orgasm. During resolution, the clitoris, labia, and vagina return to their unaroused state, usually in less than a half hour after orgasm.

The Role of Desire: Helen Singer Kaplan

Fifteen years after Masters and Johnson, sex therapist Helen Singer Kaplan published a groundbreaking book on sexual desire that built on the basic model developed by Masters and Johnson. For Kaplan, however, the first stage of sexual response was not excitement but the psychological component of sexual desire; in other words, we have to want to have sex with someone before we begin to be aroused. Dr. Kaplan described sexual response as having three stages: desire, excitement, and orgasm. She stressed that it is natural to have sexual desire, but many factors might inhibit it. For example, medications, relationship issues, past history of sexual abuse, illness, and disease all can decrease desire for sex.

Seduction and Sensation: David M. Reed

Almost a decade later, in 1989, psychologist Dr. David M. Reed developed another model of sexual response based primarily on our psychological response to sexual behaviors. He wrote that that the four stages of psychological response are seduction, sensations, surrender, and reflection, each corresponding to one of the physical stages proposed by Masters and Johnson. For many people, these phases are learned during their early sexual experiences.

Seduction refers to the stage in which people become aroused sexually and attract someone else. In the sensations phase, the senses (touch, sight, hearing, smell, and taste) extend the excitement into the plateau phase, making us want to continue these pleasurable feelings for a longer period of time. The next phase refers to orgasm—a total surrender to the passion of the lovemaking. Finally, in the reflection stage, the person examines the sexual experience. How was it? Did it bring them closer to their partner? Are they looking forward to making love again (or was it just okay—even negative)?

A Final Word

These models attempt to describe the 'typical' way that most men and women function. Many people, of course, experience their sexuality differently. And numerous issues can interfere with sexual functioning: there are specific sexual dysfunctions associated with each phase of the sexual response cycle. Even with our individual differences, however, learning more about these models can help us be more aware of our own patterns and more sensitive to the needs of our partner.

Debra W. Haffner, MPH, has been an award-winning sexuality educator for more than 25 years and was president of the Sexuality Information and Education Council of United States from 1988 - 2000. She is the author of two books for parents: From Diapers to Dating: A Parent's Guide To Raising Sexually Healthy Children (Newmarket Press, 2000) and Beyond the Big Talk: A Parent's Guide To Raising Sexually Healthy Teens (Newmarket Press, 2001).

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For more information, visit SexHealth.com.

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