And they say science isn't practical enough: German researchers believe they may have found a way to encourage fidelity. A small dose of the hormone oxytocin keeps men who are already in a relationship from straying from that relationship. Men who received oxytocin spray kept further away from attractive women during a first encounter with them than men who didn't. And the further away men stay, the less chance there is for them to get in trouble.

Oxytocin is a hormone with multiple effects that's come to be known as the love or trust hormone . Previous studies suggest that oxytocin also plays a role in maintaining monogamy in rodents. But mice are mice and men are men. The German researchers wanted a closer look at how it might affect monogamy in humans.

Since oxytocin increases trust, they expected oxytocin-dosed men to get even closer to newly-encountered attractive women. But that's not what happened.

Chemical warfare may very well be against the Geneva Convention, but all's fair in love and war.

A group of 86 heterosexual males, average age 25, received either oxytocin nasal spray or a placebo. Forty-five minutes later, the men were introduced to a female experimenter that they later described as attractive. As the woman moved toward or away from the men, they were asked to indicate when she was at an ideal distance, as well as when she moved to a distance that felt slightly uncomfortable.

Oxytocin-treated men in committed relationships tended to keep further away (4-6 inches) from the attractive woman--thoroughly unmanly behavior. This effect of oxytocin on "taken" men was the same regardless of whether the female experimenter maintained eye contact or averted her gaze, or if the men were the ones approaching or withdrawing from the experimenter.

If these results are typical, it may not be long before women won't even consider a night out without a little oxytocin along, just in case their guy's eye starts wandering. Chemical warfare may very well be against the Geneva Convention, but all's fair in love and war.

Single men (those not in a committed relationship) will be relieved to hear that they're immune from these effects of oxytocin. Uncommitted men are free to get as close as they dare to any attractive woman whose path they happen to cross, whether they're under the influence of oxytocin or not.

An article on the study was published by the Journal of Neuroscience.