THE BLOG
06/28/2010 01:22 pm ET Updated Nov 17, 2011

Why There Might Never Be Viagra for Women

A seven-year-old friend recently declared that cats and dogs are the same animal, it's just that "the dogs are the boys and the cats are the girls."

Obviously.

It's hard to deny that there's a certain canine simplicity in many men's sexual response; and a feline complexity is apparent in many women's, though this wasn't exactly what our friend had in mind. An appreciation for the nuanced nature of the female libido may have influenced some members of the FDA advisory panel, who recently voted unanimously against approval for a new drug to treat hypoactive sexual desire (depressed libido) in women. Women's sexual response is notoriously difficult to quantify, measure accurately, or predict.

Psychologist Meredith Chivers conducted research that involved showing a variety of sexual videos to men and women, both straight and gay. The subjects' genital blood flow (an indication of arousal) was monitored while they watched. Chivers found that the men were pretty predictable. The straight ones responded to anything involving naked women, but were left cold when only men were on display. Gay men were similarly consistent, though at 180 degrees.

The female subjects, on the other hand, were the very picture of inscrutability. Regardless of sexual orientation, most of them experienced increased genital blood flow whether they were watching men with men, women with women, a naked guy on the beach, a sweaty woman in the gym, or bonobos in the zoo. But unlike the men, many of the women weren't consciously aware of being turned on. Their bodies said "Yes," but their minds said, "What?"

The disconnect between what these women experienced on a physical level and what they consciously registered suggests that women's greater erotic flexibility may make it harder to know--and, depending on what cultural restrictions may be involved, to accept--what they're feeling.

Psychologist Richard Lippa teamed up with the BBC to survey over 200,000 people of all ages from all over the world concerning the strength of their sex drive and how it affects their desires. He found a similar inversion of male and female sexuality: For men, both gay and straight, higher sex drive increased the specificity of their sexual desire. Straight guys with higher sex drives tended to be more focused on women, while higher octane gay guys were more intent on men.

But with women--at least nominally straight women-- Lippa found the opposite effect: The higher her sex drive, the more likely a woman was to report being attracted to both men and women. Self-identified lesbians showed the same pattern as men: a higher sex drive meant more women-only focus. Perhaps this explains why nearly twice as many women as men consider themselves bisexual, while only half as many consider themselves to be exclusively gay.

Those who claim this just means men are more likely to be repressing some universal human bisexuality should consider sexologist Michael Bailey's fMRI scans of gay and straight men's brains while they viewed pornographic photos. They reacted as men (and dogs, with all due respect to both) tend to do: simply and directly. The gay subjects liked the photos showing men with men, while straight subjects were into the photos featuring women. Bailey was looking for activation of the brain regions associated with inhibition, to see whether his subjects were denying a bisexual tendency. No dice. The men showed no unusual activation of these regions while viewing the photos.

Sexologist Lisa Diamond spent over a decade studying the ebb and flow of female desire, finding that many women experience sexual attraction to specific people, rather than to a particular gender. She writes, "The hypothesis that female sexuality is fundamentally fluid provides the most robust, comprehensive and scientifically supported explanation for the research data."

This fundamental fluidity finds support in studies of heterosexual couples who engage in group sex or mate-swapping. They agree that it is common for "heterosexual" women to have sex with other women in these situations but that men almost never engage with other men. While we'd be the last to cite popular culture as a reliable indicator of innate human sexuality, it's probably worth noting that women kissing each other has quickly become accepted as innocent titillation in the U.S., while depictions of men kissing each other on television or films remains unusual and controversial. Most women presumably wake up the morning after their first same-sex erotic experience more interested in finding some coffee than in conducting a panicked reassessment of their sexual identity. The essence of sexuality for most women seems to include the freedom to constantly adapt to the changes life presents.

Faced with the mysteries of woman, Sigmund Freud, who seemed to have an answer for everything else, famously came up empty. "Despite my 30 years of research into the feminine soul," he wrote, "I have not yet been able to answer ... the great question that has never been answered: What does a woman want?" There is, perhaps, a liberating simplicity in women's feline complexity, which both contemporary pharmacological researchers and Sigmund Freud seem to have overlooked.

What does woman want? It depends.