revenge sex"Vengeance is an act of justice," according to the 18th-century writer Samuel Johnson, "Revenge is the act of passion."

We're talking revenge sex. It's ugly, but we all know it's out there. A guy gets dumped by his girlfriend, and it's all too easy to turn to her roommate for a little comfort and counseling. After all, what better way to show his ex not only that he's not crushed (even if he is), but that he's still an object of desire? It's immoral, petty, risky and involves an innocent party. But it happens, and men and women are almost equal-opportunity offenders: The odds a man has ever had revenge sex are 1 in 10.2. For women the numbers are 1 in 11.45.

It can take many forms, including random, meaningless hook-ups just to make the ex jealous. Some people even go for direct payback, trying to have sex with an ex, pretending to be a changed person, maybe even dangling the phrase "get back together" all before revealing in the post-coital moment, "I'm just not feeling it anymore."

Sometimes the revenge target is actually a third party. It's a safe bet that sleeping with a rival's husband is sure to upset her -- maybe even knock her off her game. And is there anything more delicious for a middle-aged woman (Meryl Streep in "It's Complicated") than to sleep with the man who divorced her years ago, while his nubile young wife (who stole him from her) fumes off camera?

According to psychology professors Cindy M. Meston and David M. Buss, authors of "Why Women Have Sex," sexual motivation is more complicated and varied than has been widely understood, and runs the gamut from altruistic to self-serving to downright mean. There's sex for love, sex for conception, sex for entertainment and, according to Meston and Buss, there's even sex to infect. As horrible as it is to contemplate, they found people who knowingly tried to pass on an STD as a vehicle of revenge.

And then there's the recent case of Therese Ziemann of Wisconsin, who, upon learning a man she was helping to support was not only married but also had at least two other lovers, went for her own variety of revenge sex. She recently reached a deal after pleading no contest to charges she lured the man to a motel, and with the help of her sister, crazy-glued his penis to his stomach. Hell hath no fury like a woman (or man) scorned. When love ends, things can get messy. Whether it's the motivation or the tool, sex often goes hand in hand with revenge.

This post was brought to you by the Book of Odds. Go check them out for more random bits of information, like this:
+ The odds a man has ever paid for sex: 1 in 6.6
+ The odds a woman has ever paid for sex: 1 in 100
+ The odds a man has ever faked an orgasm: 1 in 9
+ The odds a woman has ever faked an orgasm: 1 in 2

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