Human sexual response cycle

The human sexual response cycle is a four-stage model of physiological responses to sexual stimulation, which, in order of their occurrence, are the excitement, plateau, orgasmic, and resolution phases. This physiological response model was first formulated by William H. Masters and Virginia E. Johnson, in their 1966 book Human Sexual Response. Since that time, other models regarding human sexual response have been formulated by several scholars who have criticized certain inaccuracies in the human sexual response cycle model.

Excitement phase

The excitement phase (also known as the arousal phase or initial excitement phase) is the first stage of the human sexual response cycle, which occurs as a result of physical or mental erotic stimuli, such as kissing, making out, fantasizing or viewing erotic images, that leads to sexual arousal. During this stage, the body prepares for sexual intercourse, initially leading to the plateau phase. Physical and emotional interaction and stimulation of the erogenous zones during foreplay usually establishes at least some initial arousal.

Excitement in both sexes

Among both sexes, the excitement phase results in an increase in heart rate, breathing rate, and a rise in blood pressure. Vasocongestion of the skin, commonly referred to as the sex flush, will occur in approximately 50-75% of females and 25% of males. The sex flush tends to occur more often under warmer conditions and may not appear at all under cooler temperatures.

During the female sex flush, pinkish spots develop under the breasts, then spread to the breasts, torso, face, hands, soles of the feet, and possibly over the entire body. -->

Plateau phase

The plateau phase is the period of sexual excitement prior to orgasm. The phase is characterised by an increased circulation and heart rate in both sexes, increased sexual pleasure with increased stimulation and further increased muscle tension. Also, respiration continues at an elevated level. Masters and Johnson argue that this period must end before men can become aroused again.

Although, due to the refractory period, it is rare for men to achieve multiple orgasms, some men have reported having multiple, consecutive orgasms, particularly without ejaculation. Multiple orgasms are more commonly reported in very young men than in older men.

Resolution in females

According to Masters and Johnson, women have the ability to orgasm again very quickly, as long as they have effective stimulation. As a result, they are able to have multiple orgasms in a relatively short period of time. For some women, the clitoris is very sensitive after climax, making additional stimulation initially painful. After the initial orgasm, subsequent orgasms for women may also be stronger or more pleasurable as the stimulation accumulates.

Similarities and differences between sexes

thumb|During the sexual arousal phase, there is increased [[blood pressure in the genitals; this leads to swelling of the penis (top row), or clitoris and labia (bottom row).]]

Masters and Johnson argue that, despite some minor differences, sexual responses in both men and women are fundamentally similar. Masters and Johnson also equate a man's erection with a woman's vaginal lubrication during the excitement phase; Roy Levin states that this observation is false. A woman's clitoris is the anatomical parallel to a man's penis. As a result, clitoral swelling would be the equivalent of a man's erection.

Another aspect is the lack of concordance between subjective sexual arousal and genital arousal. Research by Meredith L. Chivers and J. Michael Bailey indicates that men tend to show category-specific arousal; that is, they are sexually aroused by their preferred gender. However, women show category non-specificity: Their genitals show arousal to both preferred and non-preferred genders. Even though women reported being subjectively aroused to, for example, a man and woman engaging in sexual activity, their genitals also show sexual arousal to two men engaging in sexual activity, two women doing so, and even non-human animals having sex.

Overall, Masters and Johnson's model appears to be a better example of men's sexual response than women's.

Criticisms

There has been much research conducted based on Masters and Johnson's model. However, inaccuracies have been found in the descriptions of the stages of sexual response. For example, Roy Levin identified a few areas of the model that had not been touched upon. First, Masters and Johnson state that only the vagina is lubricated during the arousal stage; Levin argues that the labia produce their own lubricant. Levin also presents research which shows that the first sign of physiological arousal in women is increased blood flow to the vagina, not lubrication. He also dispels information about men and their sexual response; Masters and Johnson report that pleasure was positively associated with the volume of ejaculate released, but Rosenberg, Hazzard, Tallman and Ohl gave a group of men a questionnaire and found that significantly more men reported that physical pleasure was associated with the strength of the ejaculation compared to the volume. Moreover, some researchers have found that some men can have multiple orgasms, despite what Masters and Johnson had reported.

Some researchers have also criticized how Masters and Johnson define sexual response solely in terms of physiology; for example, Everaerd, and Laan have found that sexual arousal can be defined as an emotional state in both men and women. Other researchers have stated that there is a lack of concordance between women's subjective sexual arousal and their genital arousal.

Other models

Shortly after Masters and Johnson published their book, several scholars criticized their model of the human sexual response cycle. For example, Helen Singer Kaplan argued that Masters and Johnson only evaluated sexual response from a physiological perspective, and that psychological, emotional, and cognitive factors need to be taken into consideration. As a result, she proposed her model of the sexual response cycle which includes three phases: desire, excitement, and orgasm. She argues that these three phases are interconnected, yet they have different neurophysiological mechanisms. Similarly, Paul Robinson argued that the excitement and plateau phases are the same; he criticizes Masters and Johnson's work for not clearly distinguishing when the excitement phase ends, and when the plateau phase begins.

Another model that has been put forth is the incentive-motivation model. The model explains that the desire for sex comes from an interaction between a sensitive sexual response system and stimuli that are present in the environment. Researchers argue that this model supports the idea that sexual desire is not spontaneous. Furthermore, this model implies that the case is not that one has sex because one feels sexual desire; rather, the case is that one feels sexual desire because one has sex.

Rosemary Basson proposed an alternative model of sexual response. She argues that the linear model is good at explaining men's sexual response but it poorly explains women's sexual responses; thus, she puts forth a circular model. Once they modified the pathways of the model, the circular model then became a good predictor of sexual functioning. More research needs to be done in this area to show whether the circular model more accurately describes women's sexual response.

Sexual dysfunctions

The human sexual response cycle set the foundation for studying and categorizing sexual dysfunctions in men and women. There are four main categories of sexual dysfunctions: desire disorders, arousal disorders, orgasm disorders, and sexual pain disorders. They are still categorized as such in the DSM-IV-TR. Recent research, however, suggests that the current model of sexual response needs to be revised to better treat these dysfunctions. One reason is that there is considerable overlap between sexual dysfunctions in women. One study found that in patients with hypoactive sexual desire disorder (HSDD), 41% of women had at least one other sexual dysfunction and 18% had diagnoses in all three categories (that is, in desire, arousal, and orgasm disorders).

Another issue is that, among women, there is a discrepancy between desire and arousal. After Cynthia Graham critically evaluated female sexual arousal disorder (FSAD), she found that women reported that, contrary to Masters and Johnson's model, sexual arousal sometimes preceded sexual desire; at other times, desire presented before arousal. Because of the high comorbidity rates between HSDD and FSAD, she would like to merge them to make the category "Sexual Interest/Arousal Disorder." Hartmann and colleagues summarize their views of the current model of the sexual response cycle and conclude that "by simply expanding and continuing DSM-IV criteria and the traditional response cycle classification systems, it is impossible to come to diagnostic categories and subtypes that adequately reflect real-life female sexual problems".

References

External links

Human sexual response on Discovery health
Human Sexual Response Cycles by Dr. Mitchell Tepper on SexualHealth.com
What We Can Learn from Sexual Response Cycles, Psychology Today
Blog on the Sexual Response Cycle
Classifying Sexual Dysfunctions and Recommendations for the DSM-V
Female Sexual Arousal Disorder and Its Current Issues
In-Depth Presentation on Masters and Johnson and their Contribution to Sex Research, DistinctiveVoicesBC, YouTube