- Men's physical response to sexual images (aka an erection) matches their psychological response pretty closely, whereas womens did not match very well
- Men tended to have a response very similar to their stated orientation (straight men were turned on by women, and gay men by men), but women were all over the map. I'll quote here:
All was different with the women. No matter what their self-proclaimed sexual orientation, they showed, on the whole, strong and swift genital arousal when the screen offered men with men, women with women and women with men. They responded objectively much more to the exercising woman than to the strolling man, and their blood flow rose quickly — and markedly, though to a lesser degree than during all the human scenes except the footage of the ambling, strapping man — as they watched the apes. And with the women, especially the straight women, mind and genitals seemed scarcely to belong to the same person. The readings from the plethysmograph [device to measure physical sexual response] and the keypad [to rate their subjective response] weren’t in much accord. During shots of lesbian coupling, heterosexual women reported less excitement than their vaginas indicated; watching gay men, they reported a great deal less; and viewing heterosexual intercourse, they reported much more. Among the lesbian volunteers, the two readings converged when women appeared on the screen. But when the films featured only men, the lesbians reported less engagement than the plethysmograph recorded. Whether straight or gay, the women claimed almost no arousal whatsoever while staring at the bonobos.
Interesting, no? Well there are a few ideas to explain these findings:
- Women become wet in any sexual situation to avoid suffering physical damage from sex to their vaginas.
- Women are turned on by someone being attracted to them, not another person in of themselves
Now the first hypothesis makes some sense, evolution would tend to work that way (though it does not explain the high response to women with women), but it does not explain why their physical and mental responses to sexual imagery are so different. hypothesis 2 seems to me like someone talking out their ass. Everyone is turned on by someone being attracted to them, that isn't something that can explain the difference between men and women's sexuality.
There are several ways to explain the differences that I can think of. First of all, are the differences biological or cultural? The article touches on how hard those things are to separate. We really don't know the answers to this one yet, but it is probably some sort of combination of the two, it's just a question of how much of each. Now if it's primarily biological (aka men and women are fundamentally different sexually) then we basically know why: it evolved that way, we just don't know why it evolved that way, and I don't think anyone can seriously present a good idea why it evolved that way at this point while we are still trying to decide what exactly "natural" sexuality is. Now if it's primarily cultural (aka men and women are essentially the same) then we can go two ways: either men are repressing physical responses that don't fit their psychological makeup, or women getting wet for things that don't actually turn them on.
There is another interesting possibility that I favor; Women and men could have fundamentally different physical sexual responses, but women have been forced by culture to fit into the male sexuality boxes. I certainly think that the language used to describe sexuality is very male centric. Men are usually either basically straight or basically gay (though the boundaries are to some extend fluid), whereas women have basically fluid sexuality (though they do have to some extent a sexual orientation). As a science nerd the best way to illustrate this is with a graph.
Ok, so I'm not good at making fake graphs. But the point is: in my experience women who have sort of thrown out societies expectations of them match their states desires very well with the physical one in the study. Which, in a totally unscientific manner, says to me that women are naturally* something along the lines of pansexual and it's our society that has forced them into straight or gay.
* by natually I mean that if all there was was biology. I'm a great advocate of natural != good, and the other thing is that that this is all based on distributions of people with many outliers.