The XX Factor: What women really think.

Why Women Cheat; Plus, Men With Low Sex Drives

Tim: Last week you challenged us to reveal the reasons women cheat (or want to) in response to our posts about this Philip Weiss article. I'm late to the party. But first I wanted to second Ellen's no-nonsense answer: For the same reasons men do. Desire, selfishness, the thrill of novelty, love, boredom, a boost to the ego—the list goes on.

Second, though: You second Weiss in suggesting that the female sex drive is, in the aggregate, less "pronounced," as you put it. And you write that you hear stories about women who don't want to have sex with their partners, but "[y]ou don't hear stories about men telling their wives they no longer want to have sex." But in fact, you do-at least, you do if you're a woman. I've heard this very complaint from female friends whose husbands/partners are too busy or stressed or distracted for sex. And according to some reports, like this one in Psychology Today, low male libido is reportedly on the rise, affecting some 20 percent to 25 percent of men. Meanwhile, several couples therapists—most notably Michele Weiner-Davis, author of The Sex-Starved Marriage—have suggested that male sexual apathy can powerfully affect marriages and long-term relationships. On a Yahoo Answers thread about low male libido, you'll see a post from a woman bemoaning that her male partner would rather "snuggle" and "bond" than have sex.

Now, low male libido probably has cultural and environmental causes. (Anti-depressants, estrogens, etc.) And so yeah, there may be real underlying differences in male and female sex drives in the aggregate, as you argue. But I think most women who've spent much time talking openly to other women would say that the desire for sexual novelty within a long-term relationship hardly seems to be the exclusive province of the Y chromosome. On second thought, though, maybe it's better for everyone if men still think it is.