Hockenbury Discovering Psychology 5th txtbk

332 CHAPTER 8 Motivation and EmotionHuman SexualityKey Theme• Multiple factors are involved in understanding human sexuality.Key Questions• What are the four stages of human sexual response?• How does sexual motivation differ among animal species?• What biological factors are involved in sexual motivation?Pioneers of Sex Research: William Masters(1915–2001) and Virginia Johnson (b. 1925)In 1966 Masters and Johnson broke newground in the scientific study of sexual behaviorwhen they published Human SexualResponse. Their book provided the first extensivelaboratory data on the anatomyand physiology of the male and femalesexual response. Although intended for clinicians,the book became a best seller thatwas translated into over thirty languages.Some critics felt the Masters and Johnsonresearch had violated “sacred ground” anddehumanized sexuality. But others applaudedHuman Sexual Response for advancingthe understanding of human sexualityand dispelling misconceptions.After opening a clinic for treatment ofsexual problems, Masters and Johnsonwere featured on the cover of Time magazinein 1970. They also published HumanSexual Inadequacy, in which they describedtheir innovative therapy techniques fortreating sexual problems, including the useof male and female therapist teams towork with couples. The techniques theydeveloped are still widely used in sex therapytoday. Ultimately, Masters and Johnsonpromoted a view of human sexualityas a healthy and natural activity, one thatcould be a meaningful source of intimacyand fulfillment.Psychologists consider the drive to have sex a basic human motive. But whatexactly motivates that drive? Obviously, there are differences between sex and otherbasic motives, such as hunger. Engaging in sexual intercourse is essential to the survivalof the human species, but it is not essential to the survival of any specific person.In other words, you’ll die if you don’t eat, but you won’t die if you don’t havesex (you just may think you will).First Things FirstThe Stages of Human Sexual ResponseThe human sexual response cycle was first mapped by sex research pioneers WilliamMasters and Virginia Johnson during the 1950s and 1960s. In the name of science,Masters and Johnson observed hundreds of people engage in more than10,000 episodes of sexual activity in their laboratory. Their findings, published in1966, indicated that the human sexual response could be described as a cycle withfour stages.As you read the descriptions of these stages, keep in mind that the transitionsbetween stages are not as precise or abrupt as the descriptions might lead you tobelieve. Moreover, the duration of time spent in any particular stage can vary ondifferent occasions of sexual interaction. Although it is simplified somewhat,Figure 8.8 depicts the basic patterns of sexual response for men and women.Stage 1: ExcitementThe excitement phase marks the beginning of sexual arousal. Sexual arousal canoccur in response to sexual fantasies or other sexually arousing stimuli, physicalcontact with another person, or masturbation. In both sexes, the excitementstage is accompanied by a variety of bodily changes in anticipation of sexual interaction.There is a rapid rise in pulse rate and blood pressure. The rate ofbreathing increases. Blood shifts to the genitals, producing an erect penis in themale and swelling of the clitoris in the female. The female’s vaginal lips expandand open up, and her vagina becomes lubricated in preparation for intercourse.Her nipples and breasts may also become enlarged, and the nipples become erectand more sensitive.Stage 2: PlateauIn the second phase, the plateau phase, physical arousal builds as pulse and breathingrates continue to increase. The penis becomes fully erect and sometimes secretesa few drops of fluid, which may contain active sperm. The testes increase in size. Theclitoris withdraws under the clitoral hood but remains very sensitive to stimulation.The vaginal entrance tightens, putting pressure on the penis during intercourse.Vaginal lubrication continues. During the excitement and plateau stages, the degreeof arousal may fluctuate up and down (Masters & others, 1995). During the plateaustage, the firmness of the male’s erection may increase and decrease, and so may thefemale’s degree of vaginal lubrication.