Special Guest Post by Dr. Valerie Golden

Mate poaching is a robust phenomenon, and it's here to stay. When many single women see a moderately attractive male, they are more interested in him if they believe he is already in a relationship. In fact, one study in the Journal of Experimental Social Psychology found 90 percent of single women were interested in a man who they believed was taken, while a mere 59 percent wanted him when told he was single.

Take Lisa, a young, attractive, smart, successful woman from a major metropolitan area. She professed to want and kids, desperately. So why did she waste precious time with Adam, a married father of two who never had any real intention of leaving his wife? And when they first met, was she really scanning the room for tall, dark, and handsome, or was she actually looking for married with romance sans responsibility?

Is it because a man who is already taken is more experienced? Is he seen as able to commit? Is he more desirable because another woman has pre-screened him (while single men are unknown commodities)? For some, the food on someone else’s plate always looks tastier. If someone else wants him, he must be worth wanting.

There is no simple answer. Remember, too, that some traditional types may want happily-ever-afters of emotional availability and financial security, while others may be after less than the full enchilada of marriage and children. Counterintuitive as it may seem, she might want more than a one-night stand but less than a full-fledged full-time beau that’s hers and hers alone.

It’s counterintuitive because if he’s cheating with you, honesty and trust can’t be topping your list. Nor can respect, availability, spending holidays, and family time together, or being his first priority.

Why do it?

If you're a single woman, a relationship with a man who is married gives you breathing room. You are not accountable to him if you want to see a male friend or past lover.

Plus, sneaking around has its thrills. The itself may be lustier because it’s clandestine. Having sex in the married couple’s bed, for example, becomes a daring thrill, full of lust and passion, in a way not possible otherwise. Likewise, unprotected sex. The need to be secretive, sneak around undiscovered, grabbing quick sexual encounters on the fly, can be a huge turn-on in comparison to a dinner date with a single man who calls on Wednesday night for Friday. Especially for rule-breakers, it’s just more fun being naughty. And bawdy.

Some women may have decided never to trust a man. The logic: If he has a wife at home and is cheating with me, I know he’s not me. And the sex is great because it’s new, adventurous, no strings attached, and so on.

There’s also the super-competitive woman who craves the , seeing mate poaching as the mother lode of wins to boost her . The hotter her rival, the hotter she is, the more she feels superior to the wife in terms of having the goods that men want. For these women, feeling superior has less to do with the man in question and how desirable he is, and more to do with being more powerful than and superior to the other woman.

Let’s not forget the purely carnal aspect. As long as it’s illicit and forbidden, sparks fly. If he were to actually leave his wife or partner to make this relationship permanent, brace yourself for a nosedive. For starters, he cheated on her with you, so how could you ever know he wouldn’t treat you the same way? And the sex might quickly become hum-drum once he’s available.

What about tactics? How do they do it? Mate poachers, whether they want commitment or just sex, have a range of tactics, from dissing the current partner (you deserve someone better like me) to showcasing desirable qualities that the current mate lacks (she’s cold and unfeeling; I, however, am warm, vivacious, and loving). Still, others engage in “bait-and-switch,” initially offering sex with no strings attached, only to expect down the road that her man will become so attached that he can’t bear to live without her.

We may not like the tactics, but sometimes they work and successfully.

So what can the wife do? Take these insights and understandings home. Maybe even start an affair with the husband you have. You just might discover a competitive streak you never knew you had.

Stephanie Newman, Ph.D., is the author of Mad Men on the Couch.