The Sexual Response Cycle

Instructor: Jason Nowaczyk

Jason has a masters of education in educational psychology and a BA in history and a BA in philosophy. He's taught high school and middle school

The following lesson discusses the set of physiological responses the human body undergoes during intercourse as discovered by researchers Masters and Johnson. After the lesson, test your new knowledge with our brief quiz.

Importance of Observable Data

There's a saying that goes 'seeing is believing,' and for scientists, this is especially the case. When scientists need to gather data and investigate something, observational data provides the most complete results. What if you wanted to investigate the proper hitting technique for hitting a baseball? You could ask great hitters what their preferred hitting technique is, or you could read about different hitting philosophies. However, neither of those two methods would provide as accurate of results as actually seeing different hitting techniques put into practice in real game situations.

There are some behaviors, however, that aren't as easy to observe as hitting a baseball. Some behaviors are difficult to observe because some are considered more private and taboo. Consequently, one of the more difficult sets of behaviors for a researcher to observe is sexual behavior. Sexual behavior, however, is important to observe because it provides greater insight into issues of sexuality, provides information on relationship dynamics, and provides evidence of physiological processes that the human body undergoes.

The Work of Masters and Johnson

Like food, sex is an important part of our lives. From an evolutionary perspective, the reason is obvious - sex ensures that the human species continues. Sexual behavior in humans, however, involves much more than reproduction, as we mentioned previously. Historically, much of what researchers know about sexual behavior comes from the observation of animals. Dr. Alfred Kinsey attempted to collect data on human sexual behavior through a series of interviews and surveys. This type of research was in itself groundbreaking because of its sensitive nature. However, in 1966, researchers William Masters and Virginia Johnson took research of sexual behavior a step further and published a book detailing the results of their observations of nearly 700 people who agreed to participate in their studies of sexual behavior. It might be a little uncomfortable to imagine, but all of these people actually allowed Masters and Johnson to physically observe them having intercourse and/or masturbating.

While Masters and Johnson studied many different sexual behaviors during their investigations, one of the most important products that came from their research was the development of the sexual response cycle. The sexual response cycle is a series of four physiological phases that both men and women go through during intercourse. In order to accurately observe these physiological changes, the researches carefully measured blood pressure, respiration rate, and indicators of sexual arousal such as level of vaginal lubrication in women and the level of swelling and blood flow to the penis in men. In conclusion, Masters and Johnson determined that the human body undergoes four distinct phases during sex. These phases, in order, include excitement, plateau, orgasm, and resolution.


Sexual Response Cycle
sexual response cycle

The excitement phase is the arousal phase of the sexual response cycle, and it is marked by erection of the penis or clitoris and lubrication and expansion of the vaginal canal.

During plateau, women experience further swelling of the vagina and increased blood flow to the labia minora, while men experience full erection often accompanied by pre-ejaculatory fluid.

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