Image courtesy of Danielle Corsetto at Girls with Slingshots.
Originally posted back in February, 2011:
Drs. Kim Wallen and Elisabeth Lloyd have reanalyzed some old data and found support for the idea that the closer a woman's clitoris is to her vaginal entrance, the more likely she is to experience orgasm from intercourse alone. This adds to the controversy about the nature of women's orgasms, and whether or not vaginal and clitoral orgasms are the same.
From the abstract:
In men and women sexual arousal culminates in orgasm, with female orgasm solely from sexual intercourse often regarded as a unique feature of human sexuality. However, orgasm from sexual intercourse occurs more reliably in men than in women, likely reflecting the different types of physical stimulation men and women require for orgasm. In men, orgasms are under strong selective pressure as orgasms are coupled with ejaculation and thus contribute to male reproductive success. By contrast, women's orgasms in intercourse are highly variable and are under little selective pressure as they are not a reproductive necessity. The proximal mechanisms producing variability in women's orgasms are little understood. In 1924 Marie Bonaparte proposed that a shorter distance between a woman's clitoris and her urethral meatus (CUMD) increased her likelihood of experiencing orgasm in intercourse. She based this on her published data that were never statistically analyzed. In 1940 Landis and colleagues published similar data suggesting the same relationship, but these data too were never fully analyzed. We analyzed raw data from these two studies and found that both demonstrate a strong inverse relationship between CUMD and orgasm during intercourse. Unresolved is whether this increased likelihood of orgasm with shorter CUMD reflects increased penile-clitoral contact during sexual intercourse or increased penile stimulation of internal aspects of the clitoris. CUMD likely reflects prenatal androgen exposure, with higher androgen levels producing larger distances. Thus these results suggest that women exposed to lower levels of prenatal androgens are more likely to experience orgasm during sexual intercourse.
Dr. Wallen provided some more commentary to explain what he believes in going on:
As I speculate in the paper, I suspect that the relationship between short CUMD and orgasm is not the result of moving the clitoral glans closer to the vaginal opening. In some cases it might be the case that there is increased penile-clitoral glans contact, but it may be that smaller CUMD is a proxy for the internal portion of the clitoris being forced in closer proximity to the vagina. Alternatively, or maybe in combination, smaller CUMD may be a proxy for a more diffuse clitoral eroticism. I suggest that prenatal androgen not only produces a rostral migration of the genital tubercle, but also focuses genital eroticism to a small area of the penis, primarily the area around the frenulum. Evidence from women suggests that their genital eroticism is spread over a larger area than in men. Possibly one of the effects of androgen exposure is to concentrate erotic sensation in a small area of the clitoris. Thus women exposed to higher levels of prenatal androgen have a longer CUMD and have more punctuate clitoral arousal, centered on the clitoral glans. There is a lot of research that needs to be done, but I suspect that the effects of androgens on genital differentiation are more than simply determining the final location of the genital tubercle derivatives.
He also sent along the paper, for those who are interested: download here.