Research into rape fantasies hasn't been particularly well publicized. Many people don't want to acknowledge that women have them, for fear that the news will incite or excuse real rape: "See? Women want it after all!" But I follow the Kinsey line that it's better to study the disturbing parts of human sexuality than to keep them in the dark.

So do Joseph Critella and Jenny Bivona, the researchers at the University of North Texas who published the meta-analysis mentioned above in the Journal of Sex Research in January. They combined 20 studies and a whole field of theory to evaluate eight potential explanations for women's rape fantasies. Some of the explanations overlap with each other, and others mutually contradict. Here's a summary:

-Masochism - The idea that women desire suffering. Women who engage in masochistic sex are more likely to have rape fantasies, but the great majority of women with rape fantasies do not want real rape. Accordingly, masochism may only apply to a small group of women.

-Sexual Blame Avoidance - (See my ex, above.) Women are socialized to not seek out sex lest they be considered tramps, but if they're having sex against their will they can avoid guilt. Studies comparing sexual repression to rape fantasies are mixed and overall don't support the explanation, but they may have been using wrong metrics; sexually repressed women have fewer fantasies overall but they might have a higher ratio of rape fantasies. In any case, this theory would only apply to some women.

-Openness to Sexual Experience - In some ways this is the opposite of the last one, and it doesn't explain rape fantasies so much as it describes the type of person to have them. If you're sexually open, you entertain a greater variety of fantasies. As one study described rape fantasy among these women, it's "just one more expression of a generally open, positive, unrestrictive, and relatively guilt-free expression of one's sexuality."

-Male Rape Culture - Some have argued that women have been conditioned to buy into men's fantasies of domination. But the prevalence of rape fantasies has not changed much in recent decades, even as gender roles have.

-Biological Predisposition to Surrender - In many mammalian species, the male must pursue and subdue the female in order to mate. Women may be programmed to surrender to the successful dominant male. Just like many other theories in evolutionary psychology, this one makes sense but has not been tested empirically. (Writer Tracie Egan hints at this explanation in her essay entitled "One Rape Please (To Go)" about hiring a male prostitute to play-rape her (which I recently saw her read live): "...as a girl, my equipment can be trickier to manage, therefore I need to be a boss in the bedroom to ensure I get worked the right way. [But] it gets really tiresome always being the one in charge...")

-Sympathetic Activation - The sympathetic nervous system becomes engaged in times of stress or danger, activating a fight or flight response marked by increased heart rate, respiration, pupil dilation, and genital arousal. Just like on a roller coaster, fear and excitement go hand in hand.

-Adversary Transformation - In one survey of romance novels (which tend to be written by and for women), the lead female character was raped in 54%. The male heroes are usually rugged warrior types and these books may illustrate a desire to "conquer the heart of the rapist" and tame him for marriage.

-Reaction to Trauma - This one is not mentioned in the paper, but Brett Kahr, a psychoanalyst who has conducted the largest survey of sexual fantasies ever, argues that most masturbatory fantasies are attempts to transform early difficult experiences into pleasure. So those who have been sexually abused may try to master their trauma by taming those experiences.

I asked Kahr whether it's unhealthy to entertain rape fantasies. "At one level, they pose little problem because they represent a highly normative part of female sexual fantasy," he said; many women have them, and most of these woman easily distinguish between reality and fantasy. But in some cases it may recapitulate forgotten abuse that hasn't been processed properly, or it may reflect masochistic tendencies. A woman should see a professional if she's troubled by her fantasies. Julie Shulman, a clinical psychology professor at Alliant International University who has studied rape fantasies [pdf] also told me "the sexual and emotional health of such engagement can differ greatly," and would like to see more research on the topic.

Should women share their rape fantasies with their partners? "Obviously, a loving, committed, sympathetic man would respond delicately and sensitively to such news," Kahr said, "but a more sadistic partner (with conscious or unconscious sadism towards a woman)" might use the information more destructively. "One must proceed cautiously."

I asked my friend Rachel Kramer Bussel, an editor at Penthouse who has written about rape fantasies for the Village Voice, whether she thought it was unhealthy to act them out with men. She said it's not unhealthy per se: "At the end of the day, the woman has control over it, and it can be hot to give yourself over completely to someone within that context knowing that you can trust them." Rachel added that "it's probably a tricky fantasy for men, as that is something that's inculcated into them not to do." I covered a study supporting such inhibition in the April issue of Psychology Today; it showed that men are slower to recognize words associated with dominance (coerce, fierce, etc.) if they've been primed with sex-related words (climax, oral, etc.) Pretending to rape someone, Rachel says, is "a lot of responsibility to assume, and if you're dealing with a woman who does have a history of sexual abuse in her past, it's extra thorny."