Weizman sex survey research team 311.
(photo credit: Courtesy)
Seeing another person – whether a woman or child – crying is enough to cause many men to become emotionally upset. But researchers at the Weizmann Institute of Science in Rehovot have now discovered that chemical signals found in a woman’s tears reduce sexual arousal in men when the odorless liquid is sniffed.
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Emotional crying is a universal, uniquely human behavior, but now it is clear that it has a chemical impact as well.
In a paper published online on Thursday in Science Express, the Rehovot scientists have demonstrated that some of these signals are chemically encoded in the tears themselves. Specifically, they found that merely sniffing a woman’s tears – even when the crying woman is not present – reduces men’s evaluation of sex appeal and their arousal.
The study was authored by Shani Gelstein, Yaara Yeshurun, Liron Rozenkrantz, Sagit Shushan, Idan Frumin, Yehudah Roth and Prof. Noam Sobel; they collaborated with scientists at Wolfson Medical Center in Holon.
Humans, like most animals, expel various compounds in body fluids that give off subtle messages to other members of the species. For instance, a number of studies have found that substances in human sweat can carry a range of emotional and other signals to those who smell them. But tears have no odor.
In fact, in a first experiment led by Gelstein, Yeshurun and their colleagues in Sobel’s lab in the institute’s neurobiology department, the researchers first 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 solution. The men could not.
In a second experiment, 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 tears did not influence the men’s
estimates of sadness or empathy expressed in the faces. To their
surprise, however, sniffing tears negatively affected the sex appeal
attributed to the faces.
To further explore the finding, male volunteers watched emotional movies
after similarly sniffing tears or saline. Throughout the movies,
participants were asked to provide self-ratings of mood as they were
being monitored for physiological measures of arousal such as skin
temperature and heart rate. Self-ratings showed that the subjects’
emotional responses to sad movies were no more negative when exposed to
women’s tears, and the men “smelling” tears showed no more empathy.
They did, however, rate their sexual arousal a bit lower. The
physiological measures, however, told a clearer story. These revealed a
pronounced tearinduced drop in physiological measures of arousal,
including a significant dip in testosterone – a hormone related to
Finally, in a fourth trial, the research 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
“This study raises many interesting questions, Sobel said.
“What is the chemical involved? Do different kinds of emotional
situations send different tearencoded signals? Are women’s tears
different from, say, men’s or children’s tears? This study reinforces
the idea that human chemical signals – even ones we’re not conscious of –
affect the behavior of others.”
Human emotional crying was especially puzzling to Charles Darwin, who
identified functional antecedents to most emotional displays such as the
tightening of the mouth in disgust, which he thought originated as a
response to tasting spoiled food. But the original purpose of emotional
tears eluded him.
The current study has offered an answer to this riddle: Tears may serve as a chemosignal.
Sobel notes that some rodent tears are known to contain such chemical
signals. “The uniquely human behavior of emotional tearing may not be so
uniquely human after all,” he said.