It’s official. Tears in a woman turn off men, according to new research by Israeli researchers.

The scientists, from the Weizmann Institute of Science in Rehovot, discovered that a chemical encoded within the tears reduces sexual arousal in men, and that merely sniffing a woman’s tears, even when the woman isn’t present, is enough to dampen their mood.

Crying is a universal, but uniquely human behavior. When we cry we are clearly sending out many emotional signals, but scientists have pondered the original purpose of emotional tears. Already, a number of studies have shown that human sweat can carry a surprising range of signals to those who smell it, but tears are odorless.

In their first experiment, reported online today in Science Express, Shani Gelstein, Yaara Yeshurun and colleagues in the lab of Prof. Noam Sobel in the Weizmann Institute’s Neurobiology Department, obtained emotional tears from female volunteers watching sad movies in a secluded room and then tested whether men could discriminate the smell of these tears from that of saline. The men couldn’t.

Sniffing tears didn’t affect empathy

The experiment was followed by a second. This time male volunteers sniffed either tears or a control saline solution, and then had these applied under their nostrils on a pad while they made various judgments regarding images of women’s faces on a computer screen.

The next day, the test was repeated — the men who were previously exposed to tears getting saline and vice versa. The tests were double blinded, meaning neither the men nor the researchers performing the trials knew what was on the pads.

The researchers found that sniffing the tears didn’t affect the ability of the men to decipher sadness or empathy expressed in the faces they were looking at, but surprisingly, it did lessen how much sex appeal the men attributed to the faces.

In further experiments, the scientists asked male volunteers to watch emotional movies after sniffing tears or saline. Throughout the movies, participants were asked to provide self-ratings of mood as they were being monitored for such physiological measures of arousal as skin temperature, heart rate, etc.

A dip in testosterone

Self-ratings showed that the subjects’ emotional response to sad movies was the same whether they were exposed to women’s tears or not. While they showed no more empathy than usual, however, they did rate their sexual arousal lower. Physiological tests on the men revealed a clearer picture. Men exposed to the tears showed a pronounced dip in testosterone, a hormone related to sexual arousal.

Finally, in a fourth trial, Sobel and his team repeated the previous experiment within an fMRI machine that allowed them to measure brain activity. The scans revealed a significant reduction in activity levels in brain areas associated with sexual arousal after the subjects had sniffed tears.

In the wake of this study, the researchers believe that tears may serve as chemosignals.

“This study raises many interesting questions,” says Sobel, who conducted the study in collaboration with the Wolfson Medical Center in Holon. “What is the chemical involved? Do different kinds of emotional situations send different tear-encoded signals? Are women’s tears different from, say, men’s tears? Children’s tears? This study reinforces the idea that human chemical signals – even ones we’re not conscious of – affect the behavior of others.”