Do human tears send sexual signals?

“A woman’s tears are the biggest turn-off for men,” reported The Mirror . It said the tears “contain chemicals which dampen the male sex drive”.

This news story is based on research that compared how men rated women’s attractiveness after sniffing a woman’s tears or a salt solution. Men gave lower scores to women after smelling the tears. In other experiments, smelling tears lowered men’s testosterone levels and the activity in areas of the brain associated with sexual arousal.

This was a very small study that exposed up to 50 men to tears from one of only five women. Although the researchers speculate that there is a chemical in the tears that signals to men, larger studies and measurement of the chemicals in tears are needed to confirm whether this is the case.

Where did the story come from?

The study was carried out by researchers from the Weizmann Institute of Science and the Edith Wolfson Medical Center in Israel. Sources of funding were not reported. The study was published in the peer-reviewed journal Science .

This research found that men scored pictures of women as being less attractive after they had sniffed a pad that had been soaked with a woman’s tears. It did not investigate why this was the case. According to the newspapers, the researchers speculated that it may be due to a mechanism that allows women to ward off unwanted attention from men. This theory was not tested in any way in this research.

The Mirror said that “sad tears are different to those caused by the wind of speck of dust” in their effect on men. The research collected tears from women exposed to one stimulus - a sad film - that caused them to cry. This research did not look at the effect of other types of tears, such as a response to pain or dust.

What kind of research was this?

This controlled trial looked at the effect of women’s tears on men’s attraction and sexual arousal. The researchers said that in mice, tears contain a pheromone that is a “sociosexual” signal to other mice. They said that human tears have a reflexive protective function, such as in response to dust or grit, but also form as an emotional response. They wanted to see whether human tears contained pheromones and whether a woman’s sad tears had an effect on men’s emotional and sexual response.

What did the research involve?

The researchers collected tears from two women who had watched a sad film (negative emotion tears) and asked 24 men whether they could smell the difference between these tears and a salt-water solution that had been trickled down the cheek of a donor woman.

The researchers wanted to see whether sniffing odourless tears influenced perception of other people’s emotions and the degree of attraction of men to women. The researchers pasted a small pad that had been infused with either real negative emotion tears or salt water under the noses of 24 men. The men did the test on two consecutive days, with tears on the pad on one day and salt solution the other day. The men were then shown pictures of women with emotionally ambiguous facial expressions and asked to say what emotion the women were feeling. They were also asked to rate how attractive they found the women and to complete a questionnaire assessing their empathy.

The researchers thought the tears may have failed to influence sadness or empathy in the men because the experiment (i.e. smelling a pad) was not explicitly sad. Therefore, they studied 50 men in whom they generated negative emotions by showing them a sad film while they sniffed either tears from one of five donor women or a salt solution. Measures of testosterone levels in the men’s saliva, their heart rate, breathing rate, skin temperature and sweating were taken.

To investigate whether the tears affected arousal, 16 men were then asked to look at sexually arousing pictures and films or neutral films and pictures while their brains were scanned in a functional MRI scanner. The researchers observed whether there was an increase in activity in the areas of the brain involved with sexual arousal. The men’s brains were also scanned while they watched a sad film after being exposed to both tears and a salt solution.

What were the basic results?

The men could not detect a difference in the smell of the tears and the salt-water solution.

Sniffing tears did not affect empathy scores but did affect how attractive 17 of the 24 men rated the women (p<0.02).

Watching a sad film lowered the mood of the men, but exposure to female tears did not affect how sad they felt. When they were asked about their feelings of arousal, the men exposed to tears reported lower arousal than those exposed to salt water.

Men who sniffed tears sweated more than those who sniffed salt solution. They also had lowered testosterone compared to the start of the experiment (p<0.001) before they sniffed the tears, whereas testosterone levels did not decrease in men who sniffed salt solution.

The brain scans showed that the areas of the brain involved in sexual arousal had lower activity when the men sniffed tears compared to a salt solution while watching a sad (non-sexual) film.

How did the researchers interpret the results?

The researchers said that their research: "conclusively demonstrated a chemosignal in tears”, which illustrates a “novel functional role for crying”.

The researchers said that the effects observed in the laboratory are relevant to normal behavioural responses because: “In Western culture, exposure to tears is usually in close proximity. We hug a crying loved one, often placing our nose near teary cheeks, typically generating a pronounced nasal inhalation as we embrace. Such typical behavior entails exposure equal to or greater than that experienced here, hence the effects we observed in the laboratory are relevant to human behavior."

Conclusion

This very small study in up to 50 men assessed the effects of being exposed to the tears of five women. The findings need to be repeated in a larger group of people.

The researchers say their findings mean that there may be a “chemosignal”, or pheromone, in tears that men detect subconsciously, but they highlight that they have not attempted to identify what this chemical is.

The researchers collected tears from women exposed to one stimulus - a sad film - that caused them to cry. This research did not look at the effect of other types of tears, such as in response to pain or dust. At this stage, it is not possible to speculate about the role of chemosignals within tears.