CRI听力:The Function of Tears

Nature has made the sound of a crying baby deliberately distressing. The sound makes us want to protect them.

Laboratory research has already shown that people react differently to photographs when tears are edited out, or superimposed. It completely changes the appearance of a face and the response it provokes.

But now, scientists at the Weizmann Institute of Science have shown it's not just a visual reaction. It's basic chemistry. They claim their tests show that tears of sadness temporarily lower a man's level of testosterone.

Women taking part in the study are isolated and shown sad films to make them cry, at which point their tears are collected. For the purposes of comparison, researchers also trickle saline down the women's cheeks and collect these too. Test subjects couldn't smell a difference between the real tears and the fake ones.

When men sniff the real tears, they find the women less sexually attractive than when they sniffed the saline solution. Saliva tests showed that their testosterone levels dipped simultaneously.

The scientists were surprised to find that this dip in sexual arousal didn't mean that the men became correspondingly more empathetic.

Neurobiologist Noam Sobel is leading the study.

"The chemo-signal we identified appears to reduce sexual arousal in men, due to a chemo-signal that is present in women's tears, and when men sniff this they can't smell anything perceptible but it lowers their sexual arousal. It lowers the arousal that is attributed to pictures of faces, it lowers their levels of salivary testosterone, it lowers their levels of physiological arousal and it lowers the levels of brain activity in the substrates of sexual arousal."

So, why is it that our tears have evolved a "chemo-signal" to function as a sign of sexual disinterest? According to the Weizmann team, it's possibly a mechanism to lower a man's aggression when the woman is vulnerable.

Dr. Robert Provine is Professor of Psychology in the Neuroscience department of the University of Maryland.

"It's not yet known what that substance is, that's the next critical step. What we have here is some very provocative, very interesting information. The next step is to identify what that chemical substance is and show that it, by itself can be effective."

Sobel insists the only reason they haven't previously tested men's tears is because they haven't been able to find any men able turn on the waterworks. But they've now found some good male criers.

So hopefully, they'll be able to discover whether women really are attracted to men who are more in touch with their feelings.

For CRI, I am Li Dong.