By Alexander C. Kafka

Human beings treat sex much like we do the board game Othello: a minute to learn, a lifetime to master. Fortunately, an army of researchers stands ready to take our measure and guide us in that delicate journey.

Intrepid science writer Mary Roach, who has shadowed research on cadavers and the afterlife in her books "Stiff" and "Spook," offers a fun, breezy but quite detailed account of sex research and its history in "Bonk: The Curious Coupling of Science and Sex." She straddles the border between insider and outsider reporting, offering description explicit enough to interest a physiologist but perpetually amazed and amused enough to reach those of us who don't spend all our time mulling matters like the orgasms of paraplegics, the AMS Malleable 650 Penile Prosthesis, the intercourse rates of rats wearing little polyester pants, or whether uterine upsuck (if it exists) affects fertility.

I recall one instance (in a footnote) of the "F"-word, used in the context of a chimp's digital stimulation, and lots of common slang like "wang" and "boner." But while I wouldn't necessarily give the book as a confirmation or bat mitzvah present, it generally tilts toward the tasteful when it could tilt otherwise. Fundamentally, it is, as Roach puts it, "a tribute to the men and women who dared. Who, to this day, endure ignorance, closed minds, righteousness, and prudery. Their lives are not easy. But their cocktail parties are the best."

Among those who dare: Jing Deng, of University College in London, trying (with the help of Roach and her good-sport husband, as it turns out) to capture three-dimensional ultrasound images of intercourse; Taiwanese Dr. Geng-Long Hsu, who runs the Microsurgical Potency Reconstruction and Research Center in Taipei; Ken Maravilla, a University of Washington radiology professor studying MRIs to measure blood flow to clitoral tissue during arousal; Marcalee Sipski, of the University of Alabama, who studies sexuality among those with spinal injuries and diseases; and Dr. Ahmed Shafik, of Egypt, whose revenue from surgery on "despots with colorectal issues" funds his research on sexual reflexes.

Through our vicarious visits with those and other scientists, the consistent between-the-lines motifs are the investigators' boldness and society's uptightness, even in an age of Always pad commercials about the unjust outcast status of menstruating African village girls. There has been progress, perhaps, since gynecologist James Platt White "was expelled from the American Medical Association in 1851 after inviting medical students to observe a (consenting) woman in labor and delivery" because "colleagues had been outraged over the impropriety of a male doctor looking at female genitalia." There has been progress, even, since the 1960s, when the index for the popular textbook "Essential Medical Physiology" lacked, according to sex physiologist Roy Levin, entries for the words "coitus," "vagina," "penis," "erection," or "ejaculation"—"as though," Roach writes, "sex were a secret shame and not an everyday biological event."

But even today (never mind the nonstop Levitra commercials and productions of "The Vagina Monologues"), " 'People invariably draw all these conclusions about me, about why I'm studying this,' " sex researcher Cindy Meston, of the University of Texas at Austin, tells Roach. " 'I do psychophysiological research,' " she defensively tells folks who ask what line of work she's in. " 'If they persist, I say something like, "Well, we use various visual and auditory stimuli to look at autonomic nervous system reactivity in various contexts." That usually does the trick.' "

That's an old trick, Roach reminds us. Sex researchers have long phrased their data in almost robotic terms. We don't accuse gastrointestinal specialists or brain surgeons of being voyeurs, though in some productive, essential way, they surely are, and should be. But we have a reflexive suspicion that sex researchers must "like to watch," perhaps because, primally, we do, and feel, on some level, jealous of them. So as if to assure us they aren't getting off on their work, they describe it in the dullest possible way. Roach cites, for instance, Masters and Johnson's terminology: " 'reacting unit' " (otherwise known as a couple), " 'orgasmic phase expression' " (orgasm), " 'stimulative literature' " (pornography), or " 'failure of erective performance' " (limp).

Beneath that fog of neutered naming, however, the team invented devices like a dildo camera, helping to explore "among many other things, the source of vaginal lubrication: not glandular secretions but plasma (the clear broth in which blood cells float) seeping through capillary walls in the vagina." Roach applauds:

"This, to me, is as good as science gets: a mildly outrageous, terrifically courageous, seemingly efficacious display of creative problem-solving, fueled by a bullheaded dedication to amassing facts and dispelling myths in a long-neglected area of human physiology."

Some of her historical examples are more troubling. Take Princess Marie Bonaparte, who, in the 1920s, theorized that her frigidity was due to too much distance between her clitoris and her vagina. In that take-charge management style for which the Bonapartes are known, she had her clitoris surgically moved. The results, sadly, were not satisfactory. But lest we write off the princess' preoccupation as a conceptual Waterloo, she was, it seems, onto something. " 'If the distance is less than the width of your thumb, you are likely to come,' " is Emory University behavioral neuroendocrinologist Kim Wallen's catchy synopsis of more recent data.

In Roach's exploration of female orgasm's relationship to fertility, she visits a group of friendly Danish pig-insemination technicians. While they're not averse to letting their female charges experience pleasure, they aren't particularly invested in it either.

But Roach's holy grail in this regard, "a study comparing women's conception rates following sex with and without orgasm," simply hasn't been done. Dr. Bob Nachtigall, an adjunct professor of obstetrics and gynecology at the University of California at San Francisco, explains you'd need to factor in the men's sperm counts and whether the women truly had orgasm when they conceived. Moreover, by the time couples with fertility problems reach doctors' offices, they're feeling unromantic and demoralized enough without experts telling them, as Nachtigall puts it, " 'Gee, if you had more orgasms . . .' The implication is always, 'Oh you're not doing it right.' "

Similarly elusive is the answer to the question whether masturbation would be as effective in treating female sexual dysfunction as medically recommended clitoral suction devices and the like, since the key seems to be stimulating blood flow. It hasn't been studied, Dr. Maryann Schroder, a sexologist at the University of Chicago Hospitals, tells Roach, reminding her that when Surgeon General Joycelyn Elders "suggested, in a World AIDS Day speech, that masturbation was something that 'should perhaps be taught,' " her reward was to be booted out of office by President Bill Clinton. " 'Can you imagine,' " Schroder asks, " 'if I tried to get funding for a study that had masturbation in the title?' "

There's that prudery issue again. Roach doesn't get into any systematic analysis of what studies should be, and aren't, funded, because of remaining taboos, and I wish she had. That's one of just a few qualms I have about the book. Another is that her generally enjoyable, cavalier writing style (especially in her diverting footnotes on tangents like the Victorian concern that sewing machines inspired women's wantonness) is less appealing when applied, say, to an unfortunate religious fanatic who emasculated himself. I'd say he has been through enough without Roach's little jibe about his "no doubt [making] great strides in the church choir." And a third reservation has simply to do with the book's title. Perhaps from my brief and painful turn at distance running, I associate the term "bonk" with what happens to endurance athletes when their glycogen reserves are depleted. Would this book not more aptly and currently have been called "Boink"?

But those quibbles aside, "Bonk" is a fun and enlightening go at a subject that could stand a great deal more productive investigation, in labs and in bedrooms. Meanwhile there are some tried and true lessons from which we could all gain. In Masters and Johnson's lab, the most satisfying sex was that of "committed gay and lesbian couples," Roach reports. "Not because they were practicing special secret homosexual sex techniques, but because they 'took their time,' " they empathized with and enjoyed each other's pleasure and frustration, and they talked.

Slow down. Empathize. Talk. There's some cutting-edge research we might all apply, no?

Bonk: The Curious Coupling of Science and Sex

By Mary Roach

Norton, 319 pages, $24.95