Meredith Chivers is a creator of bonobo pornography. She is a 36-year-old psychology professor at Queen’s University in the small city of Kingston, Ontario, a highly regarded scientist and a member of the editorial board of the world’s leading journal of sexual research, Archives of Sexual Behavior. The bonobo film was part of a series of related experiments she has carried out over the past several years. She found footage of bonobos, a species of ape, as they mated, and then, because the accompanying sounds were dull — “bonobos don’t seem to make much noise in sex,” she told me, “though the females give a kind of pleasure grin and make chirpy sounds” — she dubbed in some animated chimpanzee hooting and screeching. She showed the short movie to men and women, straight and gay. To the same subjects, she also showed clips of heterosexual sex, male and female homosexual sex, a man masturbating, a woman masturbating, a chiseled man walking naked on a beach and a well-toned woman doing calisthenics in the nude.

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 vaginal 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 that 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 swelled 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. Any expectation that the animal sex would speak to something primitive within the men seemed to be mistaken; neither straights nor gays were stirred by 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, 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 and the keypad 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.

...the question, first, of why women are aroused physiologically by such a wider range of stimuli than men. Are men simply more inhibited, more constrained by the bounds of culture? Chivers has tried to eliminate this explanation by including male-to-female transsexuals as subjects in one of her series of experiments (one that showed only human sex). These trans women, both those who were heterosexual and those who were homosexual, responded genitally and subjectively in categorical ways. They responded like men. This seemed to point to an inborn system of arousal.

Diamond is a tireless researcher. The study that led to her book has been going on for more than 10 years. During that time, she has followed the erotic attractions of nearly 100 young women who, at the start of her work, identified themselves as either lesbian or bisexual or refused a label. From her analysis of the many shifts they made between sexual identities and from their detailed descriptions of their erotic lives, Diamond argues that for her participants, and quite possibly for women on the whole, desire is malleable, that it cannot be captured by asking women to categorize their attractions at any single point, that to do so is to apply a male paradigm of more fixed sexual orientation.

on the other hand, keep in mind the type of woman who is going to volunteer to have a stranger put a probe up her vag while she they watch and analyze her watching porn. This is not your average girl.

Don't you think a woman who is willing to volunteer to do that is going to obviously be much more sexually open than the average girl?