Women's tears contain chemicals that dampen amorous feelings in men, suggests an Israeli study.
The sniff tests of tears, released Thursday by the journal Science, opens a new avenue for study of the role of "chemosignals" sent by sense of smell.
"Women may influence men by chemosignals, in addition to and not in place of spoken language, facial expressions or body language," says study co-author Sagit Shushan of the Weizmann Institute of Science in Rehovot. "It's not a manipulation, but rather a physiological reaction."
The study team led by Weizmann's Shani Gelstein collected tears from women watching an excerpt of the tearjerker movie, The Champ. Conducted over three years, the team tested tears from 12 women on more than 100 men in 114 sniff test experiments, where the men uniformly reported no discernible scent to the tears.
Nevertheless, compared to plain old salt water, tests with the tears induced a statistically significant drop in testosterone and other measures of sexual interest, such as pulse, in men looking at pictures of attractive women, and watching variously, sad, erotic or "neutral" (nature documentaries) film excerpts. Brain scans also show decreased activity in regions of the brain linked to arousal in men sniffing tears, as opposed to salt water dribbled over women's cheeks.
The researchers didn't try to draw any conclusions about why nature would create chemicals with this kind of effect. But, "this is a very well-controlled experiment that opens the floodgates to all sorts of scientific questions," says behavioral neuroscientist Charles Wysocki of the Monell Chemical Senses Center in Philadelphia, who was not part of the study.
In the last decade, T-shirt-sniffing studies have shown women more attracted to smells of men with different immune system chemistry, he notes, but the tears finding opens a new avenue for chemical signaling between the sexes, he says. Other T-shirt studies have shown women prefer the smell of their boyfriend's sweat.
"We are a visual species, humans are visual beings, the visual impact of seeing someone crying is going to wipe over whatever chemical effects are found in tears," says neuroscientist Thomas Mast of Florida State University in Tallahassee. "But I do think this is very cool, a good first step that needs to be repeated, and investigated."
The "most surprising outcome" was finding tears had an effect on sexual arousal, but not measures of empathy or mood, Shushan says. Inspiration for the study came from a finding of chemosignals in the tears of mice. The study team speculates that men's tears, and perhaps children's, tears, may also contain chemosignals, and hopes to conduct similar studies on them. Shushan says the team has still not concluded which chemical in tears produces the dampening effect.
"These intriguing findings hint at just how much we still have to learn about how the social world influences us, how it becomes quite literally incorporated" into the chemistry of our makeup, says psychologist Cordelia Fine, author of Delusions of Gender: How our Minds, Society, and Neurosexism Create Difference. "We tend to think of hormones as driving us to think, feel and act in particular ways, and this study is a nice reminder that the relationship between hormones, brain, and behavior isn't a one-way street."
By Dan Vergano