The reproductive importance of orgasm in men is obvious because of its association with ejaculation and the motivating effect of the pleasure of orgasm. In women, the role of orgasm is less clear and women vary in their capacity for orgasm and in the frequency with which they experience it. This is therefore a key factor in the variability of women’s sexuality.
In the Global Survey of Sexual Attitudes and Behaviors, that used computer-assisted telephone interviewing and postal questionnaires to assess sexual problems in 9,000 women aged 40-80 years, the prevalence of “inability to reach orgasm” ranged from 17.7% (in Northern Europe) to 41.2% (in Southeast Asia). Kinsey et al. (1953) found that 9% of women reported having been unable to ever experience orgasm. Lloyd, in her book on female orgasm, included a table on orgasm rates during coitus obtained across a number of studies; the percentage for women who reported “always” or “almost always” experiencing orgasm during coitus ranged from 12-59%.
Women also vary considerably in the age at which they first experience orgasm. A recent survey showed that 23% had experienced orgasm by the age of 15, 53% by age 20, 77% by age 25, and 90% by age 35. There has probably been some shift towards earlier first experience of orgasm since then, because of the lessening of socio-cultural suppression of women’s sexual pleasure (Baumeister, 2000). This point will be considered further in the next section on masturbation.
In the U.S. National Health and Social Life Survey (NHSLS) was reported that, during the previous year, 29% of women always experienced orgasm during sexual activity with their partner. Women’s rates of orgasm consistency (defined as “usually or always” experiencing orgasm) were higher during masturbation than during sexual activity with a partner. About 60 percent of women reported that they “usually” or “always” had an orgasm when masturbating, compared with 29 percent during partnered sex (the corresponding figures for men were 80% and 75%).
This reflects considerable variation in the ease with which women achieve orgasm. Some women can experience orgasm from fantasy alone, or from breast stimulation or stimulation of other non-genital areas. Other women require specific forms of genital stimulation. In some women this requires direct stimulation of the clitoris, in others, stimulation of the anterior vaginal wall, leading Freud to postulate that there were clitoral and vaginal orgasms, the first being an immature form. This generated a lot of controversy before being refuted. The idea that there are different types of orgasm has persisted, however; Singer proposed that there were two types, which he called “vulval” and “uterine,” reflecting the patterns of sensation experienced during the orgasm. There is now good evidence that many women require clitoral stimulation to reach orgasm, and although the proportion that report that they always experience orgasm during intercourse varies across studies, it is usually a minority. We should keep in mind, when striving to understand the function of women’s orgasm, that women are not anatomically constructed to receive clitoral stimulation during vaginal intercourse.
The issue of the female orgasm has therefore generated a considerable amount of debate and controversy over the years. Another debate has been whether female orgasm has any reproductive relevance. There are some who have argued that orgasm enhances fertilization, and that it is, as such, an evolutionary adaptation . Lloyd wrote a critique of this literature and made the convincing case that these proposals of “adaptation” were all examples of “bias in the science of evolution.” She concluded by supporting Symons’s “by-product” explanation i.e. orgasm is a response pattern necessary in the male for reproduction, but remaining as a potential response in women because there had been no evolutionary reason to suppress it. We will return to this “by-product” concept below. Further evidence to support Lloyd’s position comes from a classical twin study by Dunn that investigated orgasmic responsiveness in 4,037 women. Comparison of identical and non-identical twin pairs showed an estimated heritability of 34% for difficulty reaching orgasm during intercourse and 45% for difficulty reaching orgasm during masturbation. Two additional studies have explored the role of genetic influences on variability in female orgasmic function in non-clinical samples of women. Another researcher Dawood reported that genetic influences accounted for approximately 31% of the variance of frequency of orgasm during sexual intercourse, and 51% of the variance of frequency of orgasm during masturbation. More recently, personality factors and their associations with female coital “orgasmic infrequency” in a sample of 2,632 women from the same UK twin register were investigated. Introversion, emotional instability, and “not being open to new experiences” were associated with orgasmic infrequency. While these results are intriguing, the authors themselves acknowledged that their assessment of orgasm was quite limited and these studies require replication. However, the results point to a definite genetic influence in some important aspects of orgasmic potential. Such genetic variability would not be likely to occur if orgasm was important for female fertility.
It was proposed that it is sexual arousal that is most important for conception, with its vaginal tenting and pooling of semen providing the optimum environment for the capacitation of sperm. Orgasm, in contrast, is likely to prematurely terminate this environment. Overall, there is no evidence that orgasm in women has any enhancing effect on women’s fertility. The question of whether women who are unable to experience orgasm are less fertile than orgasmic women has not yet been studied.