What Do Women Want?: Adventures in the Science of Female Desire (5 page)

Why, from beginnings in equally obscure academic publications, had parental investment theory come to permeate cultural assumptions over recent decades while monkey realities, ancestral facts, remained much less known? We embraced the science that soothed us, the science we wanted to hear.

“T
his organ serves a pleasure god,” Jim Pfaus said. He held a plastic replica of the human brain in his hands. A Van Dyke beard and a hoop earring adorned his animated face. His expertise as a neuroscientist and his Concordia University labs were called on by the major pharmaceutical companies whenever they wanted to test, in rats, a new drug that might serve as an aphrodisiac in women—none had worked out in women so far. His labs sat in a university basement. There he studied his rats in a variety of cages and, in a surgical theater, removed their brains—about as big as a person’s thumb from the middle knuckle to the tip.

Pfaus was obsessed with rat ways of seeing and feeling, learning and lusting, and when he wanted to investigate, say, exactly which set of neurons were sparked by a type of stimulation, by copulation-like prodding of the cervix or by the excitement of glimpsing a desirable male, one method was to provide a female rat with the experience, kill it, extract and freeze her brain, place the organ on a device resembling a miniature cold-cut slicer at a delicatessen, and shave off a specific, infinitesimally thin cross section. Peering at the slice through a microscope, he could pinpoint recent neural activity by noting the tiny black dots that told him where certain protein molecules—by-products of cell signaling—had been manufactured.

It was due to one woman that Pfaus—in his spare time the lead singer in a punk band called Mold—had been drawn to his specialty. Until the late seventies, scientists didn’t study desire in rat females; they didn’t see it; it didn’t exist: as with the rhesus, scientists fixated on what the rat female did in the act of sex, not what she did to get there. And what she did in the act was go into paralysis. She froze in a position called lordosis, with her spine slung low and her butt cocked high, so the male could penetrate. Rat intercourse required female rigor mortis. It was easy to understand the female as absolutely passive, without will, a vessel whose involuntary perfume pulled the male in. Similar scientific ignorance had pervaded our idea of females across the animal kingdom, with “receptivity” being the key term.

But then Martha McClintock, like Wallen, helped take scientists deeper. McClintock had begun to make herself famous years earlier while still an undergraduate at the all-women Wellesley College. She built a case that women living in close proximity responded to each other’s hormonal scents, causing the timing of their menstrual periods to converge, and her work was published in the revered journal
Nature
. Soon she was calling attention to female rat solicitations, to the female’s specific hops and darts, her head-pointings and prancings away—her methods of inciting the male to put his forepaws on her flanks; to set his paws into the whir of flank-patting that instantly immobilized her, as though by hypnosis; and to slide himself into her. While Pfaus and I talked about this in front of a bank of his Plexiglas cages, one of his females went further, as regularly happened. Dealing with a stolid, sexually uninterested male, she stood behind him, mounted his backside, and humped, as though to put ideas in his head. How, Pfaus marveled, could science not have noticed this?

McClintock documented, too, that the female, if her cage allowed her to evade her partner, made sure to slip away from him, constantly, in the midst of his pumping, so the sex didn’t end too quickly for her. Under any circumstances, in rat as in 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 unmistakably what she craved. This went on and on and on.

As we watched, Pfaus mentioned the anatomical oversights that had squelched our understanding of the clitoris—rat and human—until a decade before. The organ has sizeable extensions, lying internally in the shape of bulbs and wings. These are positioned, in part, just behind the front wall of the vagina. Yet these nerve-rich formations had gone mostly unnoted by modern anatomists, who either left them undrawn or gave them no import. Science seemed almost to have willfully diminished the organ, cutting it metaphorically away. It was another lesson in the minimizing of women’s desire. Then, beginning in the late nineties, Helen O’Connell, an Australian urologist, detailed the organ’s sprawl, its many inches in reach. And she championed its sensitivity to pressure through the vaginal sheath—sensitivity perhaps responsible for vaginal climaxes and possibly the explanation for the fabled and debated G-spot. O’Connell was blunt about the averted eyes of her scientific predecessors. “It boils down,” she said, “to the idea that one sex is sexual and the other is reproductive.”

Now Pfaus pulled apart his plastic model of a human brain, his fingers in the folds. He spoke about the neurotransmitters that define eros for women as well as men. The libido is, in a sense, two-tiered. There’s the lower realm, in which hormones rise up from the ovaries and adrenal glands, float along the bloodstream to the brain, and fuel the production of the brain’s neurotransmitters. How exactly this fueling happens is still a mystery; so is the quantity of fuel needed to keep the production line running well. The higher realm is the brain itself, the domain of the neurotransmitters. These biochemicals, not the lowly hormones, form the essence of lust.

Dopamine—its atoms arranged like an antennaed head with a spikey tail—is, in a way, the molecular embodiment of desire, its main chemical carrier. It isn’t only that; it speeds through a multitude of the brain’s subregions and exists in infinite relationships with other neurotransmitters and has all sorts of effects, from motor control (the trembling and sluggishness of Parkinson’s patients stem from a shortage of dopamine) to memory. But dopamine is the substance of lust. And by way of his mini deli slicer, Pfaus had narrowed his sights on two tiny territories at the brain’s primal core, the medial preoptic area and the ventral tegmental area. These were the heart of dopamine’s sexual system, he said, “the ground zero of desire.”

From this primitive epicenter, dopamine radiates outward. “A dopamine rush is a lust-pleasure,” Pfaus continued. “It’s a heightening of everything. It’s smelling a lover up close—a woman inhaling that T-shirt. It’s starting to screw; it’s wanting to have; it’s wanting more.”

Yet for the excitement of dopamine to fix on an object, for it to be felt as desire rather than as a splintering into attentional chaos, it has to work in balance with other neurotransmitters. Serotonin plays an indispensable part. Unlike dopamine’s keen drive, he said, serotonin dampens. Unlike dopamine’s lust, serotonin instills satiation. Flood female rats with antidepressants—like the selective serotonin reuptake inhibitors, the SSRIs—that bolster serotonin, and the females will spend less time courting males. They will also bend their spines less fully, raising their butts less completely, to accommodate the males they do mate with.

It was important, Pfaus emphasized, to understand serotonin’s virtues. They go beyond keeping depression at bay. The neurotransmitter also allows the brain’s frontal lobe, more precisely the prefrontal cortex, the region of planning and self-control, to communicate effectively within the organ, to exert what’s known as executive function. Serotonin reduces urgent need and impulse; it facilitates sensible thoughts and orderly actions. The problem, though, is that if serotonin is too strong in relation to dopamine, a woman making love is likely to find herself thinking about the next day’s schedule rather than feeling overtaken by sensation and craving. But with serotonin and dopamine in the right balance, erotic energy will be neither displaced by tomorrow’s to-do list nor permitted to fracture into chaos. With the frontal lobe and the libidinous core in harmony, desire can have both form and force.

For all the agility of his deli slicer, which could be set to the width of a micron, Pfaus was nowhere near to completely capturing the interplay of neurotransmitters. But a third type of transmitter essential to eros, he said, are the opioids, which surge with orgasm and also spike in tandem with dopamine’s drive, so that glimpsing a lover’s muscular chest or reading a paragraph of erotica offer a minor wave of opioid bliss. Describing this pleasure, he talked about the opioids’ most potent varieties, the products of poppies: morphine, heroin. Send these drugs into the brain and satisfaction is so thorough—so much stronger than serotonin’s well-being—that inertia takes hold. Both the executive region and the lustful center are quelled; direction and drive are nullified. In the less potent forms supplied by orgasm, the opioid rush lulls to lesser degrees. Meanwhile, a paradoxical process kicks in. Even while the opioids are quieting motivation, they are preparing the brain to be motivated again by somehow stoking the dopamine system. Orgasms simultaneously subdue the brain and teach it to seek more climaxes. Maybe even regardless of orgasm—for Pfaus couldn’t be sure his female rats were climaxing—he saw the power of opioid bliss in his lab. Infuse female rats with a chemical that blocks this ecstasy, and they lose their desire to have sex at all.

Pfaus, whose hoop earring cast a gleam, whose mind bounced always between rodents and humans, translated this finding into a few words of advice: men had better perform; they’d better learn, they’d better deliver, and they’d better keep on delivering.

Not that this would solve men’s problems, not that it should calm their worries. One morning he lectured his undergraduates on the Coolidge effect, a standard in sexuality textbooks, an expression of what Pfaus scorned as evolutionary psychology’s “shtick.” The Coolidge effect comes from a tale that goes like this: One day President Coolidge and his wife were visiting an experimental government farm. They took separate tours. When Mrs. Coolidge came to the chicken yard she noticed the rooster’s frequent mating and asked the attendant how often this went on. “Dozens of times each day,” he informed her, to which she replied, “Please tell that to the president when he comes by.” The attendant did as she requested when the president arrived. “Same hen every time?” the president asked. “Oh, no,” the man answered, “different hen every time.” And the president said, “Please tell that to Mrs. Coolidge.”