What Do Women Want

monkey sex, the animals attach, copulate, detach, and reattach repeatedly until the male ejaculates. The female rat, experiments showed, likes to prolong the process, to make it last longer than the male otherwise would. All of this, the solicitations and the preference for more drawn-out intercourse, suggested will and desire.
    And McClintock established that by controlling the pace of mating, by getting the protracted stimulation and the rhythm that pleases her, the female can raise her odds of getting pregnant. She can raise them a lot. The extra thrusts, Pfaus said, cause contractions that aid sperm on their way into the uterus. And the deeper thrusts—for the male rat, forestalled from ejaculating, starts to pump harder—plies or jolts the cervix in a way that leads to a hormonal release that then helps to sustain a fertilized egg.
    Pregnancy, though, is not an animal motivation, as McClintock and Pfaus, like Wallen with his monkeys, saw clearly. This was a critical point. Animal species have been designed by evolution to perpetuate themselves, to reproduce, but in the individual animal, it isn’t reproduction that impels. The rat does not think, I want to have a baby. Such planning is beyond her. The drive is for immediate reward, for pleasure. And the gratification has to be powerful enough to outweigh the expenditure of energy and the fear of injury from competitors or predators that might come with claiming it. It has to outweigh the terror of getting killed while you are lost in getting laid. The gratification of sex has to be extremely high.
    Pfaus had been following the early light shone by McClintock. Partly because of her research, he saw that a rat’s brain was not merely a brain but a mind, that a rat’s psychological experience could be a revealing version of our own. An array of experiments, of brain shavings, of injections of chemicals that boosted or blocked one neurotransmitter or another, of observations of rats making choices in all sorts of carefully constructed habitats and scenarios, fed his knowledge. One line of studies building on McClintock’s work used a special cage with a Plexiglas divider down the middle. The divider had holes just big enough for a female rat—but not a male—to squeeze through. A female could determine the pace of sex by slipping from one side of the partition to the other and back again. “Female rats do what feels good. With the divider, she’s having better sex. Better vaginal and clitoral stimulation. Better cervical stimulation.” He described a study showing that intercourse stimulated the rat’s clitoris: a colleague had painted males with ink, then charted the inky areas on their mates. About orgasms, Pfaus couldn’t be sure whether female rats were having them; there was no easily measured sign, like ejaculation in males, to mark subjective explosion. But about pleasure and very intense desire, he was certain.
    Proof ran like this: If, right after a rat finished a long-lasting session of mating, she was placed alone in another chamber, she would associate the new chamber with the sex she’d just had. Next, when given a choice between this new chamber and yet another, she would spend her time in the one linked with mating. She would make this choice even if the alternate chamber was set up to be much more inviting in other ways—even if the alternate space was dark, speaking to the nocturnal rat’s sense of safety, while the chamber linked with pleasure was brightly lit, screaming of mortal danger. Run the same test with a female who’d just had quick—unsatisfying—intercourse and she would, afterward, opt for the dark space.
    One of Pfaus’s graduate students had lately performed and filmed a straightforward demonstration of desire—of motivation derived from the learned expectation of reward, just as desire develops in humans. Sitting with me in his office a few floors above his rat chambers, Pfaus played the video. The student picked up a female rat and, with a tiny brush, stroked the clitoris, which protruded from the genitalia like a little eraser head. She stroked a few times, then put the animal back down in her cage. Swiftly the creature poked her nose out of the open door. She clamped her teeth on the white sleeve of the student’s lab coat and tugged the woman’s hand inside the cage. The student brushed the rat’s clitoris again, set her down again. And again the rodent bit into the sleeve, pulling, communicating