6 scientific american mind may/June 2011

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Women may have a more subtle way of telling men “no” than anyone imagined. Chemical cues in their tears signal that they are not interested in romantic ac tivities, according to a study pub­lished online January 6 in Science.

Crying reveals a person’s mood, but its evolutionary origins have long been a mystery. Because emotional tears have a different chemical makeup than those evoked by irritants in the eye, cognitive neuroscientist Noam Sobel of the Weizmann Institute of Science in Rehovot, Israel, wondered whether emotional tears relay chemical mes­sages to others.

Sobel and his research team col­lected tears from self­professed “easy criers” as they watched sad movies.

Later, the researchers held jars con­taining the odorless tears and pads that had been dipped in the tears under men’s noses.

These men rated female faces as less sexually attractive than did men who sniffed saline. Moreover, their sexual excitement dropped, as indi­cated by their own reports and by

levels of testosterone in their saliva.The researchers then scanned the

men’s brains as they watched a tit­illating movie scene using functional MRI. Brain regions associated with sexual arousal showed less activity in men who sniffed tears compared with those who sniffed saline.

The findings represent the first evidence that human tears send chemical messages, Sobel reports. Because a decrease in testosterone levels is linked to reduced hostility, he speculates that weeping dampens not only the libido but also violent behavior. “If the signal really lowers aggression toward you, then the evolutionary value of crying is clear,” he says. —Janelle Weaver

One of the few exceptions to the old saying “everybody is afraid of something” is a 44-year-old woman known to psychologists as patient SM. She suffers from a rare case of brain damage to an almond-shaped region of her brain called the amygdala that, according to a paper published online December 16 in Current Biology, makes her incapable of experiencing fear.

For three months researchers did everything they could to scare SM. “We tried to use stimuli common in Western society,” says Justin Feinstein, a University of Iowa graduate student who worked on the study. They showed her horror movies, walked her through haunted houses and exposed her to all kinds of other situations that the average person would consider frightening. They dug through her past, questioning her about times when she had been held up at knifepoint and gunpoint and nearly killed in a domestic dispute. Not once in any of these situations did they find evidence that SM felt afraid, by her report or via observation.

They found instead that situations that would terrify most people evoked in SM an intense feeling of fascination. At one point they took SM to a pet store to see how she would behave around snakes, an animal she had earlier told them she hated. When she saw the snakes, she was immediately drawn to them. She even picked one up and began playing with its tongue. When asked to explain her behavior, she said that she was overwhelmed with curiosity.

These findings suggest that our emotional response to

danger involves elements of both fear and fascination. When we find ourselves in potentially threatening situations, Fein-stein explains, “the amygdala helps us navigate the fine boun-dary between approach and avoidance.” If the amygdala is functioning properly, these emotions work together to get us out of trouble—and enable us to enjoy the occasional grue-some movie. When it is damaged, however, our response can actually work against our survival, attracting us to the very things we should be avoiding. As the researchers concluded, “the evolutionary value of fear is lost.” —Joe Kloc

>> emotions

Fascinated by FearResearchers get a rare glimpse at life without fright

>> evoLutionary BioLogy

Crying Women Turn Men OffWeeping releases a chemical that reduces sexual arousal

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