National Geographic News
A woman crying.

An Alaskan woman weeps in Prince William Sound (file photo).

Photograph by Natalie B. Fobes, National Geographic

Christine Dell'Amore

National Geographic News

Published January 6, 2011

Read it, but try not to weep, ladies—your tears may lower your man's sex drive, according to a new study.

Crying linked to emotions—perhaps a uniquely human behavior—is poorly understood by scientists.

However, previous research has shown that in mice, tears communicate information through "chemosignals," causing scientists to speculate that human tears could serve a similar function.

(See "Mouse Tears Are Aphrodisiacs.")

Such chemical communication would not be a surprise, since humans are already "supremely good" at expressing themselves verbally and via body language, according to study co-author Noam Sobel, a neurobiologist at the Weizmann Institute of Science in Israel.

Though it's too early to know exactly what human tears are saying, one interpretation may be that a woman's emotional tears lower males' testosterone levels, thereby reducing aggression—and by default, sexual arousal.

"Put in the bluntest of ways, we've identified the chemical word for 'no,'" Sobel said.

Cry Me a River—Of Research

In multiple experiments, male subjects smelled either women's fresh tears—collected after the women had seen a sad movie—or a control liquid of saline, which was trickled down the faces of the same women.

The scientists first determined that neither liquid has a discernible odor to men.

When the men were shown photographs of ordinary women not involved in the experiment, those who had sniffed real tears were less sexually aroused than men who had sniffed saline—as revealed by the men's heart rates, skin temperatures, and testosterone levels, among other cues. (Explore an interactive human body.)

Men who had sniffed women's tears also said they felt less turned on by the pictures than men who had sniffed saline, although the reported effect was more modest than that seen in the objective tests.

A final experiment using magnetic resonance imaging (MRI) of the men's brains backed up this finding. Men who had sniffed real tears had less activity in parts of the brain linked to sexual excitement.

The experiment was double-blind—neither the subjects nor the scientists knew which liquid was which—a technique considered especially strong in research science.

Lower Sex Drive Just Part of the Story?

Sobel cautioned that, so far, this trail of tears may be leading his team to only part of the story.

For instance, it's possible that the men's lack of sex drive is just a side effect of the drop in testosterone provoked by the tear chemical—and the signal is perhaps really meant to reduce aggression.

In evolutionary terms, the ability to control aggression in another animal can have major value, Sobel pointed out.

A "beautiful example" in the animal world involves blind mole rats, some of which emit tears and rub them all over their bodies—a strategy that seems to keep hostile mole rats at bay, he said.

"It's like it's protecting itself against aggression. I'm willing to bet that's perhaps a similar picture [to what] we're seeing here," said Sobel, whose study will be published tomorrow in the journal Science.

Sobel noted that the tear signaling is likely not tied to gender, but rather to dominance: Less dominant people may be sending aggression-reducing messages to stronger individuals via their tears.

His team next plans to replicate their study with men's tears.

Women's-Tears Study Needs "Excavating"

The tears study is a "very powerful" development, said Martha McClintock, founder of the Institute of Mind and Biology at the University of Chicago and a pioneer in human chemosignal research.

(Related: "Pheromone in Urine Spurs Mating in Elephants.")

But McClintock cautioned against speculating too early about what the tear chemosignals may be saying.

"We need to excavate it some more—you know there's something there but don't know the full shape of it and how it works," she said.

"Now let's look to see what are the effects of men's tears and babies' tears and grandparents' tears— what's the effect on people at all different stages of their lives," she added.

"Let's not just stop and say this is something that's only important in a sexual context."

5 comments
Christina Fenn
Christina Fenn

gypsies tears are pretty powerful but i think that's because of all the magic in 'em

Trinh Dinh
Trinh Dinh

I really dont like a too emotional guy. It even drives me crazier when seeing them crying.

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