As any man with the slightest experience knows, a woman's tears are powerful tools, eliciting abject apologies, unexpected confessions and urgent begging of "Honey, stop, please." But one thing they are not, is sexy.
Now a team of Israeli neuroscientists think they know why. Emotional tears shut down male desire.
In a study published Thursday in the journal Science, the Weizmann Institute of Science researchers collected emotional tears from female volunteers by showing them sad movies. Then they had male test subjects sniff the actual tears and fake tears comprised of saline.
A whiff of the real deal caused testosterone levels in the men to drop significantly. They found pictures of women less sexually attractive. When the men were sent into brain scanners, and shown a sad film, the men who were exposed to the fake tears didn't show much lower activity in a region associated with sexual desire, but the activity in the same region was greatly reduced in men who breathed real tears.
The brain scans, the big yawn over alluring pictures and the drop in the he-man hormone led the scientists to conclude that "women's emotional tears contain a chemosignal that reduces sexual arousal in men."
The scientists haven't determined which component in blubbering tears caused the men to go limp, but "a major effort currently being carried out is to isolate the active component of the tears that exerts the physiological effect," Sagit Shusan, one of the study authors, said.
"Emotional" tears are different from tears caused by, say, an eye irritation, prior research has shown. Kari Green-Church, an expert in protein analysis at Ohio State University, has identified scores of tear proteins. "The function of proteins are wide-ranging," she said. Some defend the eyes against germs, some are hormones. Emotional tears from post-menopausal women are different from those of pre-menopausal women. In one experiment she conducted, her team ran samples from grad students and found "a protein unique to pregnancy and it turned out the women was pregnant."
Other researchers also have detected proteins associated with emotions: They've found dopamine and serotonin in tears, as well as prolactin, the desire-squelching hormone that spikes right after a man ejaculates and sends him running to watch SportsCenter rather than sticking around to cuddle.
Bottom line, ladies? If you're looking for arousal, don't turn on the waterworks.
Update: Nightly News covered the study, too: