"Don't knock ," Woody Allen famously quipped. "It's sex with someone I love."

But masturbation has, of course, been knocked around some, historically. According to Thomas W. Laqueur, a professor of history at the University of California at Berkeley (and the author of Solitary Sex: A Cultural History of Masturbation) masturbation was not a topic of great interest to the powers that be until 1712, when a con man named John Marten anonymously published a book spectacularly entitled: Onania; or, The Heinous Sin of Self Pollution and all its Frightful Consequences, in both SEXES Considered, with and Physical Advice to those who have already injured themselves by this abominable practice. And seasonable Admonition to the Youth of the nation of Both SEXES.

In this book, he first introduced the idea that the biblical Onan's sin was masturbation, even though most close readers of the biblical text know Onan's actual sin was a failure to impregnate his dead brother's wife (as mandated by Jewish law)—specifically, coitus interruptus.

The book became a hit, and Marten, now fancying himself a "surgeon," quickly capitalized on his luck by selling remedies for the ills of masturbation. Con men are, above all, great capitalists, as we have all re-learned recently in the U.S.

The book, it appears, had hit a nerve by tapping into the zeitgeist of a cultural shift, where concerns about privacy were becoming paramount. Masturbation, along with reading printed books—a new technology at the time—had become a symbol for the uncontrolled, uncensored private lives of individuals, including women. Such private power was felt to threaten the social order. The social keepers of the order—the politicians, aristocrats, and professional classes—hence hurried to proclaim the potential dangers embodied in this newly shamed and shameful act.

It wasn't long before physicians began decrying masturbation as the root cause of disease, dysfunction, and poor character. Children were threatened with the most horrible fates if they were to engage in it. himself had his qualms about continued masturbation into , but at least he recognized that early masturbation, and the feelings and events surrounding it, was a person's introduction into . and around masturbation could color a person's adult sexuality. Freud famously concluded a 1912 symposium on masturbation for the Psychoanalytical Society in Vienna by saying, "I think the time has come to break off. For we are all agreed on one thing—that the subject of masturbation is quite inexhaustible."

Through the 19th century, the assault on "self-abuse" continued: Reverend Sylvester Graham invented the Graham crackers to curb sexual impulses. In the 1830s, Benjamin Rush, a renowned physician and signer of the Declaration of Independence, argued that masturbation caused tuberculosis, loss, and epilepsy. J.H. Kellogg, turn of the century medical writer and creator of breakfast cereal, believed signs of masturbation included acne, weak back, and convulsions. Noted 19th-century physician and early sex research pioneer Richard von Krafft Ebing linked masturbation to and other types of what he considered deviance and illnesses.

Interestingly, masturbation was not considered proper or safe for women even during those times when some were given masturbation treatments by their doctors. Yes, in the late 19th century, doctors occasionally masturbated women who were suffering from "hysteria.'" It was a nifty Victorian trick: Suppress and deny female sexual knowledge and expression, and when the resulting misery erupts through general manifestations of bodily and emotional discomfort, diagnose the women as ill and have them get sexual release through the desexualized digital (and later mechanical) manipulations of male physicians. All in a day's work!

By the 60s and 70s, the tide had begun to turn. The publication of Kinsey's and Masters and Johnson's research revealed that masturbation was both common and harmless. Many studies have since confirmed this basic truth, revealing, in addition, that masturbation is neither a substitute for "real" sex nor a facilitator of risky sex. Masturbation may promote comfort with one's genitalia, enhancing both orgasmic capacity and condom use. Educated people, it turns out, masturbate more, and have better sex lives. A recent study even reported that masturbation may protect men against prostate cancer. (But you're unlikely to see a government-sponsored public relations campaign promoting this particular preventative strategy.) Given these data, you'd think the controversies would be put to rest. But you'd be wrong.

In my human sexuality class recently, I asked students to come up with all the known slang terms for male masturbation. They quickly listed at least a dozen. Then I asked them to come up with slang to describe female masturbation. None came instantly to mind. After much effort, they came up with "flicking the bean" and "Jill off." That was it.

Language describes reality, and also shapes it. What you don't have words for you do not own or understand. This observation is supported by the data. According to the research, over 95 percent of males have masturbated to by age 20, compared to around 60 percent of women (with some studies suggesting an even larger gap).

The discrepancy with regard to masturbation is doubly problematic because masturbation, it turns out, is a particularly important predictor of sexual health and for women, more so than for men. One of the best predictors of whether a woman will be able to achieve orgasm in her sexual relations is a history of masturbation in adolescence.

Why such a gap? One reason may be men's higher sex drive. If you define sex drive as preoccupation with sexual behavior and thoughts, including sex crimes and , then men routinely manifest higher levels of it than women. Such elevated interest may lead to higher masturbation rates. Structural differences may also play a role. A penis is highly accessible and regularly handled in the act of urination, which may lead to greater familiarity with its potential uses.

But biology, while being necessary, is never sufficient to explain human behavior. Our behavior is determined by a complex interaction between our biological heritage and cultural context.

Biology, for example, has prepared girls to give birth at 15, but our culture tells them not to, and most obey. Biological evolution works by killing the young before they reproduce. Our culture routinely works to save even the weakest babies. Society, in other words, can shape the impact of any biological tendency or difference. Our society has chosen not to work to minimize the masturbation gap; in fact, it may be contributing to it. Men, after all, are socialized toward self-reliance and unabashed search for sexual pleasure. Such qualities in women are still regarded with much ambivalence.

It need not be so. If we can shed the misinformation of the past in so many other areas, surely we can do so here as well. In a way, the gap in masturbation resembles the well-known historical gap in salary. Both are useless and unfair remnants of a dated social consciousness. The fair and data-based message for today's young women should be clear: Get to know your sexual body; get to know it and love it so you may, in time, teach your partner to do the same. Save your guilt for real transgressions, like exams.

The masturbation gap needs to close. Will it? Keep an eye on the slang...