THURSDAY, Jan. 6 (HealthDay News) -- Crying may be nature's way
of telling men to give women some space: A new study indicates the
smell of women's tears considerably dampens men's sexual
Research by Israeli scientists examining the significance of
emotional human tears suggests they are far more than watery drops
squeezed from glands around the eyes. Women's tears play a
functional role by emitting chemical signals that reduce
testosterone levels and sexual arousal in men, the study found.
Men's and children's tears have not yet been analyzed, according
to researcher Noam Sobel, of Israel's Weizmann Institute of
Science, who hopes to learn if the tears from these groups also
send biological signals to others.
Earlier studies had established that emotional tears contain
different molecules than tears produced from cutting onions, for
example, or those protecting the eyes from debris.
"The fact that emotional tears are different in content was a strong clue for us that they served as a chemo-signal," said Sobel, a professor of neurobiology at the institute. "For sure, it's a means of chemical communication. We communicate in many ways."
In a series of experiments, Sobel and his fellow researchers
first determined that men could unconsciously distinguish between
the smell of women's tears -- which have no discernable odor -- and
odorless saline solution.
The 24 participants then viewed emotionally ambiguous pictures
of women's faces, rating the sadness and sexual attractiveness of
each. For 17 of the men, the faces appeared less sexually
attractive after sniffing tears than after sniffing saline.
Fifty men later watched a sad film after sniffing either tears
or saline, which produced a modest drop in self-rated sexual
arousal and a pronounced drop in salivary testosterone levels in
those who sniffed tears.
Lastly, MRI brain images of 16 men shown sexually arousing
pictures and movies indicated that those who sniffed tears
beforehand had lower activity in brain regions that typically show
activity during arousal.
"I think this study makes overall sense because every emotional response must have been developed for an evolutionary advantage," said Dr. Alan R. Hirsch, founder and neurological director of the Smell & Taste Treatment and Research Foundation in Chicago.
"Testosterone also affects levels of aggression, so if you reduce the degree of aggression, you enhance the survivability of the woman," added Hirsch, noting that eventual clinical applications could potentially be used for sex offenders or those with sexual aggression problems.
The study was published online Jan. 6 in
Sobel said the findings could spur further studies that identify
the active compounds in tears and examine if chemo-signals in
women's tears signal anything other than sexual disinterest.
"Now we want to identify the molecules that have the effect," he said. "Hopefully in a few years we'll have some good, strong answers."
The American Academy of Family Physicians has information on
emotions and health.