TEARS of sadness contain a chemical turn-off for men, diminishing their sexual arousal by smell alone.
In a pilot experiment, Noam Sobel and colleagues at the Weizmann Institute of Science in Rehovot, Israel, asked a group of men to sniff tears before filling out a mood questionnaire. 鈥淭o our surprise, we found no change in the area of positive or negative mood, but there was a decrease in sexual arousal,鈥� says Sobel.
To investigate further, Sobel鈥檚 team collected tears shed by two women watching sad movies. They then soaked small cotton pads in the tears, or in saline which had been dripped down the women鈥檚 faces.
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A group of 24 male volunteers were unable to smell the difference between the tears and saline. The men were then asked to rate the sexual attractiveness of a series of photographs of women鈥檚 faces 鈥� once with the tear-soaked pad placed under their nose, once with the saline and once without any pad.
The team found that ratings of sexual attraction were lower when the men sniffed the real tears. The smell of tears had no effect on the perception of sadness in the pictures.
To see whether a sad mood might affect sexual arousal in a similar way, the team swapped the photographs for a sad film and measured testosterone levels in saliva samples. They found that testosterone levels dropped 鈥� an indicator of lowered sexual arousal 鈥� both during and after the film, but only when the men smelled the tear-soaked pads.
Finally, the team investigated whether tears had an impact on markers of sexual arousal in the brain. Sixteen men watched sexually arousing films while Sobel鈥檚 team recorded their patterns of brain activity using fMRI. They then compared this activity with that which occurred while the men watched sad, happy or emotionally neutral films and sniffed either saline or tears. Again, the scent of tears proved to be a turn-off for the men, who showed less activity in areas associated with sexual arousal when smelling the tears (Science, ).
鈥淭he evidence of tears as both chemosensory and visual signals indicates they can operate in both light and darkness,鈥� says Robert Provine at the University of Maryland, Baltimore County.
That tears should lower arousal comes as a surprise to Ad Vingerhoets at Tilburg University in the Netherlands, who points to evidence that male mouse tears contain a chemical that boosts sexual arousal in female mice. 鈥淚 can鈥檛 believe that the reduction in sexual arousal is the main purpose [of emotional tears], but regard it as a mere side effect of lowered testosterone, which also acts to reduce aggression,鈥� Vingerhoets says.
Sobel maintains tears could be useful in lowering arousal in men. 鈥淲e鈥檝e identified the word 鈥榥o鈥� in the language of chemical communication,鈥� he says. 鈥淲e know that women cry more during menstruation, when it鈥檚 not an effective time to conceive.鈥�
鈥淲e have identified the word 鈥榥o鈥� in the language of chemical communication鈥�
The finding falls short of providing evidence for the existence of human pheromones, as the team did not measure a change in actual behaviour, and they were unable to identify the exact chemical eliciting the effect.