She showed the short film [An image of Bonobo Chimps mating] to men and women, both straight and gay. She also showed them clips of heterosexual sex; male and female homosexual sex; a man masturbating; a woman masturbating; a chiselled man walking naked on a beach; and a well-toned woman doing callisthenics in the nude...
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The genitals of the volunteers were connected to plethysmographs — for the men, an apparatus that fits over the penis and gauges its swelling; for the women, a little plastic probe that sits in the vagina and, by bouncing light off the vagina walls, measures genital blood flow. An engorgement of blood spurs a lubricating process called vaginal transudation: the seeping of moisture through the walls. The participants were also given a keypad so they could rate how aroused they felt.

The men, on average, responded genitally in what Chivers terms “category specific” ways. Males who identified themselves as straight became aroused while gazing at heterosexual or lesbian sex and while watching the masturbating and exercising women. They were mostly unmoved when the screen displayed only men. Gay males were aroused in the opposite categorical pattern.[Guessing that means the same, except with women instead of men]

Any expectation that the footage of animal sex would speak to something primitive in the men seemed mistaken; neither straight nor gay men were stirred by watching the bonobos. And for the male participants, the subjective ratings on the keypad matched the readings of the plethysmograph. The men’s minds and genitals were in agreement.

All was different with the women. No matter what their self-proclaimed sexual orientation, the women 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 as they watched the apes, though to a lesser degree than during all the human scenes, except the footage of the ambling, strapping man. And with the women, especially the straight women, mind and genitals seemed scarcely to belong to the same person. During shots of lesbian coupling, heterosexual women claimed 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.

Meana spoke broadly and not only about her dyspareunic patients when she said: “Female desire is not governed by the relational factors that we like to think rule women’s sexuality as opposed to men’s.’’ She finished a small qualitative study in the past year consisting of long interviews with 20 women in marriages that were sexually troubled. Although bad relationships often kill desire, she argued, good ones don’t guarantee it. The generally accepted therapeutic notion that for women, incubating intimacy leads to better sex is, said Meana, often misguided. “Really, women’s desire is not relational, it’s narcissistic,’’ she said. It is dominated by the yearning to be the object of erotic admiration and sexual need. Still on the subject of narcissism, she talked about research indicating that in comparison with men, women’s erotic fantasies centre less on giving pleasure and more on getting it. “When it comes to desire,” she added, “women may be far less relational than men.”

Like Chivers, Meana thinks of female sexuality as divided into two systems, but conceives of those systems in a different way to her colleague. On the one hand there is the drive of sheer lust; and on the other there is the impetus of value. For evolutionary and cultural reasons, she believes women might set a high value on the closeness and longevity of relationships: “But it’s wrong to think that because relationships are what women choose, they’re the primary source of women’s desire.”