If you have a pulse then you've spent more time than you'd care to admit suspecting or contemplating cheating. Even if you've never officially done it, every single last one of us has let a glance linger a beat longer than necessary or allowed an office flirtation to reach a state of "friendly" that would make our significant other suspicious.

Redbook writer Dana Hudepohl gathered up a roomful of relationship experts and basically slashed every cheating cliche we'd relied on to rock us to sleep at night—starting with "People cheat when they're unhappy at home."

Not so. In fact, according to a survey by the late Shirley Glass, Ph.D., noted infidelity researcher and author of NOT "Just Friends" about half of men cheat when they're "happy" or "very happy" in their current relationship.

I know this won't shock the skivvies off you, but the survey and other studies have confirmed that sometimes all men need is a wink and a nod to be unfaithful---like Chris Rock says, "A man is only as faithful as his options." Even if they're happily married with a fulfilling sex life, says Tina Pittman Wagers, Psy.D., a clinical psychologist and instructor at the University of Colorado at Boulder.

This, however, isn't a trait men and women statistically share. In the same survey by Glass, the majority of women reported feeling unloved and unappreciated for at least a year or more before cheating on their husbands.

However, for some, the cheating takes place before even the first year mark.  Contrary to what you may envision as the most common extramarital affair—one that happens when you're both middle-aged, sexually bored and starved for excitement—as of late, the most common time is youth.

"More people have affairs the first two years of marriage than any other time," says Barry McCarthy, Ph.D., a marital therapist and author of Getting It Right This Time: How to Create a Loving and Lasting Marriage. In fact, McCarthy thinks temptation toward straying is such an overwhelming part of being human, that rather than assign yourself as the type who would never cheat, you should be a bit more practical.

"Here's the best way to prevent affairs," he says. "Rather than saying, 'We will never have one,' instead think of the kind of person, situation and mood that would make you vulnerable."