Why guys cheat on hot women: some men can't stay faithful, even when they're already with gorgeous girls. Cosmo investigates this baffling behavior.(Hot Topics)

When the news broke that actor Ethan Hawke had an extramarital tryst while shooting a film in Canada, it was hard not to wonder if he'd gone insane. What other reason could there be for him to risk losing his wife, Uma Thurman, an A-list movie star and uberbabe, for a 22-year-old no-name? Although we don't know the behind-the-scenes details of their marriage, infidelity experts say it's not surprising that guys like Ethan indulge in sideline action. "Several factors make some men more likely to stray, even if they are dating or married to a beautiful woman," says Don-David Lusterman, PhD, author of Infidelity: A Survival Guide. And as it turns out, the reasons they're unfaithful are rarely about the sex itself but rather that cheating fuels a deep psychological need.

The first factor at work is the man's level of success. Guys in high-profile, powerful positions--such as celebrities, business executives, and politicians--often have a sense of superiority and entitlement. "These guys have achieved a certain status, and bedding several attractive women further reinforces it in their mind," says Lusterman. Moreover, these men are constantly on the road, away from their girlfriends and wives. At the same time, their prominence attracts a slew of babes who offer no-strings-attached sex. "They may have a wonderful partner waiting at home, but the situation they're in, coupled with their role of pursuer, makes it that much easier to cheat," adds Lusterman.

But celebs aren't the only snakes. Plenty of regular Joes are unfaithful too, especially when their backgrounds condone it. According to Shirley Glass, PhD, the recently deceased author of Not "Just Friends" Protect Your Relationship From Infidelity and Heal the Trauma of Betrayal, ...