A team of Israeli scientists is reporting that when your date at the movies starts crying, it may have an effect on you even if you can't see the tears.
Seeing tears clearly has an effect on people -- it tends to turn anger into compassion. But scientists at the Weizmann Institute of Science wondered if the effect was strictly visual. Might there be some chemical in human tears that was responsible for the urge to care for someone? So they advertised for people willing to donate tears.
"We got mainly female donors," says biochemist Idan Frumin, one of the authors of the new study.
On each day of testing for the study, researchers collected fresh tear samples by showing women tear-inducing films, including these:
And we'll add our own title to the mix -- this tear-jerking scene from Titanic.
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He says the first step was to see whether smelling a woman's tears had a measurable effect on men.
Researchers had their female tear donors watch sad movies. They then took a few drops of a woman's tears and had men sniff them to see if the tears had any recognizable smell.
"They don't," says Frumin.
Although they didn't smell anything, Frumin and his colleagues asked the men to look at pictures of women's faces and to fill out a questionnaire.
"One of the questions in the questionnaire was: 'What is the state of sexual arousal of this specific subject in this specific moment?' And to our amazement, we saw a drop in arousal," he says.
Communicating With Chemicals
That prompted them to do several more studies, and the findings were consistent: Testosterone levels went down and brain areas involved in sexual arousal were quiet after men sniffed a woman's tears. None of those changes occurred when men sniffed salty water that had been dribbled down a woman's cheek.
As they report in the journal Science, Frumin and his colleagues say there must be some chemical in human tears causing this effect.
"It's probably the best study yet showing that chemical communications between humans is a reality," says Thomas Cleland, a psychologist at Cornell University.
Cleland says it shouldn't be surprising that humans can communicate with chemical signals. Animals clearly do it; it's just been hard to prove for humans.
Other Chemical Signals
But psychologist James Cherry of Boston University says though the Israeli study convinces him that there is some chemical signal, he isn't convinced the chemical is only in the tears.
"Certainly there are effects," he says. "But whatever substance or substances that may be there could be found in a lot of places. You just don't know that." Cherry says the chemical could be in sweat or saliva.
Psychologist Ad Vingerhoets of Tilburg University in the Netherlands has also been studying human tears. He says women's tears may reduce male testosterone and sexual arousal, but that's not the main effect.
"It's my hypothesis that tears [have] an effect not primarily on testosterone but on oxytocin," says Vingerhoets, referring to the hormone that promotes social bonding and caregiving.