Tears mean a lot of things in the drama of human interaction. They telegraph heartbreak, hopelessness, anger, frustration, elation and relief. They express mood — and can alter behavior — in an instant.

But it turns out there might be more to know about tears, which historically have interested poets more than scientists.

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The Israeli researchers have only studied women’s tears so far. But they suspect men’s tears, and possibly children’s, also contain chemical signals. They are eager to find out what messages those tears may convey. The Associated Press

A team of Israeli researchers believes that tears, in addition to everything else they convey, send a sexual message that can be summarized as “Now’s not a good time.” In a study published online Thursday by the journal Science, the researchers report that men who sniff tears cried by sad women experience a temporary decline in both sexual arousal and circulating testosterone, a hormone tied to libido.

“We’ve identified that there is a chemo-signal in human tears,” said Noam Sobel, the researcher at the Weizmann Institute of Science who headed the study.

Only women’s tears have been studied so far, but the researchers suspect men’s tears, and possibly children’s, also contain chemical signals. They are eager to find out what messages those tears may convey.

“This experiment opened gazillions of questions. It opened way more questions than it answered,” Sobel said.

The new study places human tears in a family of fluids that includes urine and the secretions of anogenital glands. Those fluids contain behavior-altering compounds, known as pheromones. Emotional tears have a different chemical composition from tears shed when the eye is irritated. But the identity of the ardor-quenching substance they contain isn’t known.

The study, which required a complicated process of collecting tears and then exposing people to them in a controlled manner, was greeted positively in the small circle of researchers who study crying.

“It’s the first report. I think it’s quite interesting,” said Robert Provine, a psychologist and neuroscientist at the University of Maryland Baltimore County, who has studied tears as a visual cue.

“The results indeed are fascinating,” said Ad Vingerhoets of Tilburg University in the Netherlands, who has studied the social reactions to crying.

In the new study, Sobel and his colleagues collected tears from women who cried after watching a sad scene in a movie. The researchers beforehand trickled saline solution — salty water — down the cheeks of the women and collected it as a “control” substance. A group of men were then exposed to the two liquids by sniffing them in vials and, for some of the experiments, by having a small pad soaked with the liquid taped between the nostrils and the upper lip.

The men were unable to distinguish the two liquids; both were odorless. However, the men’s physiological states, and to some extent their thoughts, changed depending on whether the liquid was tears or saline.

For example, when presented with emotionally ambiguous pictures of women’s faces, 17 of 24 men in the experiment found the faces to be less sexually attractive after sniffing tears than after sniffing saline. After watching a sad movie and sniffing tears during it, they also reported an overall reduction in sexual arousal.

These subjective changes were small. Slightly larger were changes in physiological measurements.

Testosterone concentration in saliva (which reflects the amount circulating in the bloodstream) fell 13 percent after sniffing tears but stayed the same after sniffing saline. Physiological state, as measured by skin temperature, heart rate and respiration, also fell after exposure to tears. Functional MRI imaging of the brain also showed less activity in areas associated with sexual arousal after smelling tears.

Taken together, the results “suggest that women’s emotional tears contain a chemo-signal that reduces sexual arousal in men,” the researchers concluded. “We have … identified an emotionally relevant function for tears.”

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