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A man would be unwise to wish tears to flood from their female lover. Unless that man is Justin Timberlake, of course. He had his reasons.

The thing is, there's scientific evidence to suggest a women's tears can have a negative effect on men's sexual desire. Female tears contain a "chemical signal" that reduces arousal in men, according to a study at the Weizmann Institute in Israel.

Before we go any further, we should say that the research comes from 2011. Our attention was peaked when we saw the information reignited today on Twitter thanks to the QI Elves.

Obviously, the 'fact' sparked a little reaction. Some people dismissed the information entirely on account of the study relying on the existence of 'pheromones,' which has been disputed.

But according to Professor Noam Sobel, who led the original study at the Weizmann Institute, there's a lot of evidence to say that women's tears really do impact men.

Upsetting

(Image: Getty)

Prof Sobel told BBC World Service radio that the "chemical signal" apparently stimulated in tears decreased levels of testosterone, as well as brain activity associated with sexual arousal.

The research experiment that brought this view involved scientists collecting tears from women volunteers, who cried while watching sad films. Maybe Titanic? Up hadn't come out yet.

Male volunteers then had the tears, or a placebo salt solution, placed under their noses on a pad while being shown images of women's faces. The men weren't told whether they'd been given tears or salt. The participants then swapped tears for salt solution, again unknowingly.

Sniffing tears

(Image: Getty)

According to the Weizmann Institute findings, men who sniffed tears found women less sexually appealing.

It seemed that the levels of testosterone - a hormone related to sexual arousal - in the men's saliva fell by 13 per cent on average after they sniffed tears, but was unchanged by the salt water.

Researchers also said that the men's physiological state, measured by skin, temperature, heart rate, and respiration, also fell. MRI brain scans showed less activity in 'sexy' areas of the brain too – but only post-tear sniffing.

Scientists also mentioned that male volunteers couldn't distinguish between salt water and tears – both were odourless and the same colour and constistency.

"This study reinforces the idea that human chemical signals - even ones we're not conscious of - affect the behaviour of others," Prof Sobel said in online journal Science Express.

"Fascinating"

(Image: Getty)

Of course, the study isn't conclusive. It was supported by others, but questioned too.

"I think the study has used sound methodology and the results indeed are fascinating," Ad Vingerhoets, from Tilburg University in the Netherlands, told Nature at the time.

"But as far as I know, there is no clear logical, theoretical or empirical justification to design a study on the effects of tears on sex."

There have been thoughts that the crying-sex impact could be linked to evolutionary theories on neural effects on behaviour. Simply, ideas that crying prompts feelings of sympathy and care.

Robert Provine, from the University of Maryland, explained that that the results were consistent with previous suggestions that crying could reduce aggression.

Some think that testosterone could be connected to hostility and anger – tears might dampen those feelings. And, it seems, they could dilute sexual desire too.

Crying a river, as Justin Timblerlake once encouraged, could spell the end of humanity, then. Upsetting.