How Women's Tears Unman a Man

They lower the concentration of testosterone

It's widely held that a woman's tears will turn a man to mush. And many think that sympathetic response is a sign of sensitivity, a psychological shift away from baser male impulses.

But new research suggests that much of the response may be involuntary and that men are unable to help themselves. The smell of a woman's tears, the study found, is associated with a dip in testosterone, the principal male hormone, and a general decline in sexual arousal. 

Not only is a decline in testosterone  associated with a decline in sexual arousal, but, probably more importantly, it is associated with a decrease in aggressive behavior.  This, more than a decrease in sexual arousal, is likely the evolutionary driver for this phenomenon.  A decrease in aggression towards women is likely to prevent some woman's deaths in the long run, a powerful force for evolution.

"Emotional tears" are considered by many biologists to be uniquely human. They're known to have a different chemical composition than tears shed when the eye is simply irritated. The few studies of tears' psychological effects suggest they have a help-soliciting function.

Read the article; how they did the study is quite interesting, but more than I wish to quote. Just this hint:

To conduct the study, the research team posted an ad on the Weizmann Institute campus seeking volunteers who could cry easily. About 60 women and one man responded. They were screened to see how easily they cried and to determine the volume of tears they produced.

"We reached this core group of six women criers who could come back to the lab every other day and cry a full" milliliter, Sobel said.

Each woman chose a movie to elicit crying, watching it in private and collecting tears. By far the most successful tear-inducer was the death scene in "The Champ," a 1979 film starring Jon Voight about an over-the-hill boxer making a comeback to provide a better future for his son, whom he is raising on his own.