Masters and Johnson were primarily interested in studying the biology of sexuality (i.e., what happens when you have sex) and so in the late 1960s they set up a lab and actually observed individuals engaging in sexual behavior. Their work resulted in the establishment of the Sexual Response Cycle which continues to shape the way in which we view sexual functioning, even today. The Sexual Response Cycle is thought to include at least three phases: 1) Sexual Desire, 2) Sexual Arousal, and 3) Sexual Orgasm. Our present sexual disorder classification system relies upon these three distinct phases of the sexual response cycle.
The Sexual Desire Phase includes thoughts, fantasies, and motivation to engage in sexual activity. The second phase, Sexual Arousal, includes both physical and subjective arousal as described earlier. Subjective sexual arousal includes the subjective appraisal of "feelings" of being sexually aroused or "turned on," whereas physical sexual arousal refers to objective, physical indicators of sexual arousal. Both men and women experience increased muscle tension, respiration rate, heart rate, blood pressure, and vasocongestion as physical indicators of sexual arousal. Vasocongestion refers to the engorgement of blood vessels. For men, vasocongestion produces a penile erection, swollen testes, and the scrotums moves up towards the body. For women, vasocongestion leads to the swelling of the clitoris and vaginal lips, vaginal lubrication, and enlargement of the uterus. The third phase, Sexual Orgasm, begins once arousal reaches its peak intensity (heart rate, respiration, and blood pressure increase sharply) and is discharged in a series of muscular contractions in the pelvic region. For most men, and some women, ejaculation occurs at this time. In men, ejaculation is simply the release of ejaculatory fluid which consists of prostate fluid and semen. While the vast majority of men ejaculate during orgasm a small minority of men do not. Additionally, it is not uncommon for a man to occasionally have a "dry" orgasm. Female ejaculation is a bit more complicated. Some women report ejaculating upon orgasm and researchers have yet to agree exactly what female ejaculate is composed of. Some researchers have identified the fluid as being nothing more than urine while others have found it to have a compound that is quite similar to prostate fluid.
In the 1960's, Helen Singer Kaplan, Ph.D. added a fourth phase to Masters' and Johnson's Sexual Response Cycle. This fourth phase was called the Resolution Phase and refers to the physiological changes that are produced when sexual arousal subsides and one returns to their pre-sexual state. These phases of the sexual response cycle were originally proposed as a linear model meaning that desire must precede arousal, and arousal must precede orgasm, in a fixed linear sequence. This model is very important because at present, we define and classify sexual dysfunction as consisting of an interruption in one or more of Masters' & Johnson's three original phases of the sexual response cycle. In fact, the Diagnostic and Statistical Manual 4th Edition, Text Revision (DSM-IV-TR: APA, 2000) stipulates that sexual dysfunction includes three important components: 1) a disruption in one of the phases described above, 2) distress regarding the disruption, and 3) a disturbance in interpersonal relationships. If all three criteria are fulfilled, then we can talk about the individual's experience in terms of a disorder. More on how sexual disorders are classified and diagnosed follows in the section called Disorders of the Sexual Response Cycle.
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While, Masters' and Johnson's work during the 1950's has received praise for their noteworthy and trail-blazing contributions to the field of sexual science (and certainly that praise is well-deserved), recent research has identified problems with their original model. Basson (2005) has proposed that this model may be problematic when we consider female sexuality because the female sexual response cycle may be quite different than the male sexual response cycle. As mentioned above, Masters and Johnson proposed the Sexual Response Cycle as a linear model. In linear models, there is a beginning point, (Desire Phase) and a specific sequence of events that follow which lead to an end point (Orgasmic Phase). In Masters' & Johnson's Sexual Response Cycle, Desire is followed by Arousal, which is followed by Orgasm. While this linear model does appear to be accurate for men, it does not seem to adequately describe the female response cycle. Basson proposed an alternative to this linear model to describe the female sexual response cycle. Basson notes the female sexual response cycle is not linear and is better described as circular. Women may not necessarily experience desire first. Instead, they may not be thinking or fantasizing about sex at all, but once they are approached and sexually stimulated by their partner, they may become aroused and desire may result.
While a large portion of the research conducted by Masters and Johnson was devoted to studying the physiology of the sexual response cycle, they also made recommendations for couples experiencing sexual dysfunction. A treatment developed by Masters and Johnson that is still prescribed today by sex therapists is called sensate focus. The main goal of sensate focus is to help the couple reconnect with each other and to learn about one another. Specifically, the couple is encouraged to engage in touching (both erotic and non-erotic) so that they can learn what they each like. However, since Masters' and Johnson's revolutionary work during the 1950's, a major shift has occurred in how sexual dysfunction is understood and treated. Namely, sex has become medicalized (Pacey, 2008). What was once approached from a psychological standpoint is now approached from a medical one. In fact, while Masters' and Johnson's work emphasized the psychological factors that contributed to sexual dysfunction, new medical advancements have allowed providers to bypass these psychological factors and associated treatments and to use medical interventions, regardless etiology. Treatment has moved away from psycho-social therapies that addressed the presumed causes of sexual dysfunction (e.g., relational problems and/or traumatic sexual history) to medications that treat the symptoms of sexual dysfunction, regardless of its cause. Leading to the next question, "Can Viagra © cure all?"