The Genetics of Female Orgasms
In both studies, the sample consisted of 2,914 women who had participated in the Australian National Health and Medical Research Council Twin's registry. These included 638 pairs of identical twins, 343 pairs of same-sex fraternal twins, and 948 women with opposite sex fraternal twins or whose twins did not participate. The ages of the women ranged from 19 to 52, with a mean age of 31.1. In addition to basic demographic information, the women were asked how often they experienced orgasm from penis-in-vagina intercourse, during other forms of partnered sex such as oral and manual stimulation, and from masturbation, with the options being never, rarely, (less than 20% of the time), fairly often, (20-40% of the time), often, (40-60% of the time), usually, (60%-80% of the time), almost always, (not specifically defined but let's say 80%-99% of the time), and always.
For penetrative intercourse, the numbers for frequency of orgasm for all groups (according to the first paper) were 13.7% never, 21% rarely, 14% fairly often, 11.5% often, 13.1% usually, 17.9% almost always, 5.3% always, and 3.7% do not do. For other forms of intercourse, the numbers were 13.6% never, 19.8% rarely, 13.5% fairly often, 10% often, 11.3% usually, 16.5% almost always and 10.4% always (5.0% n/a). For masturbation they were 10.8% never, 7.0% rarely, 4.5% fairly often, 3.9% often, 4.7% usually, 10.7% almost always and 27.2% always (31.1% n/a). The numbers in the more recent paper are slightly different, but it is presented in graph format and lacks the do not do, category, so it is hard to tell if the differences are due to updated survey information or a slightly different calculation of percentages that excludes those respondents who do not participate in an activity (the largest differences are in the masturbation category, so I am guessing it is the latter). The surveys did not distinguish between clitoral and vaginal orgasms or look at average number of orgasms, which are aspects that are probably also affected by genetics, and of course it relies on self-reporting, which is never perfect even when respondents are guaranteed anonymity, but the data obtained are nonetheless a good start to understanding the genetic and environmental factors that affect women's tendency to orgasm.
In the initial analysis, the researchers found that genetic factors would account for 31% of the variance in the frequency with which women experienced orgasms during penetrative sex. Genetic factors also appeared to account for 37% of non-penis-involving forms of intercourse and 51% of variance during masturbation. That last number is the most revealing, in my opinion, since masturbation eliminates partner skill as a factor. Nobody knows your body and the ways it responds to stimulation better than you. And if you have trouble bringing yourself to climax then chances are good it is not just a matter of technique (although there are of course exceptions, especially given the hush-hush policy of our culture surrounding female masturbation).
The follow-up paper looked at the correlation between a number of other factors and orgasms rates, to further illuminate what factors affect women's rates of orgasm. They looked at personality traits, including impulsivity, extraversion, neuroticism and psychoticism. They also looked at traits likely to affect the women's sex lives such as marital status, lifetime number of sexual partners, attitudes toward sex, risky sexual behavior, libido, frequency of fantasies, and masculinity, whatever that means. Socioeconomic traits looked at were education, occupation and social status. They also looked at childhood illness and maternal stress during pregnancy, on the theory that such factors might affect sexual physiology. The correlation between all of these traits and rates of orgasms were too weak to account for more than 1% of the variation between women (in most cases the correlation was too weak to explain even that much). For PIV-sex the only correlation with any significance was libido. Libido was also the strongest trait correlated with orgasm rate for other forms of stimulation, but this is pretty clearly a case where correlation and causation are impossible to untangle. These traits, especially the sexual ones, did show slightly higher correlation with rates of orgasm during masturbation, but again the correlations were small.
In other words, the big conclusion of the two papers is that, of the traits studied, genetics had by far the strongest impact on women's frequency of orgasms, beating out even environmental factors that we might naturally assume would have a strong impact, such as attitudes toward sex. There might still be other factors that the researchers did not take into account, but genetics are clearly too major a contributor to ignore. As the authors of the research state in their conclusion, "Normal variation in female orgasm rate is large, heritable, and mostly unrelated to other traits."
Dr. Pisaster has a doctorate in biophysics, not actually anything sexy. She does however enjoy having sex, reading about sex, and talking about sex. Especially when she's had a little whiskey.