Why Do People Cry?

A team of Israeli researchers has put forth yet another in a long line of fascinating theories as to why humans tear up. Casey Schwartz on how crying may have helped us evolve as a species.

Why certain emotions bring tears to the eye and how this has helped us trudge along as a species are two questions science has still not managed to resolve. But Israeli researchers at the Weizmann Institute of Science recently made a quirky new contribution to the litany of theories as to why human beings cry.

Published today in the journal Science (and online on Thursday), the research team led by Dr. Noam Sobel found that women's tears act to dampen the sexual inclinations of the men who smell them. One psychologist not associated with the study theorized to the Los Angeles Times that this may be a tool for women to ward off unwanted advances.

Evolutionary psychology has puzzled over the question of what is it about crying that would have been advantageous for survival.

Tears have proved extraordinarily elusive for science, which hasn’t cracked the crying code, leaving the question still standing: What is the reason for this behavior?

In the new Israeli study, 24 men were recruited as subjects. They were given one of two vials to sniff, identical in appearance. One vial contained tears collected as they dripped down a donor’s cheek; the other contained saline, that had also been dripped down the donor’s cheek, to mimic any smell from their skin or lotion that would have influenced the tear sample.

The men doing the sniffing were not told what was in the vial, and reported that the liquid was odorless. Researchers then poured a bit of liquid from the vial onto a cotton pad and pasted it onto the subject’s upper lip, where it remained as they were shown a series of photographs of women’s faces. They were asked to rate how sad they perceived the faces to be—and how sexually attractive they found them.

Each subject went through this process twice, once being given a saline vial, once a vial of actual tears. They saw the same photographs both times, and of the 24 men, 17 reported finding the faces in the photos less sexually attractive after they’d smelled tears than after they’d smelled only saline. It’s a surprising finding, one that Dr. Noam Sobel interprets in evolutionary terms. Sobel’s assumption is that something in emotional tears, as yet unidentified, acts as a “chemicosignal” to produce a lowering of arousal among present company.

What a stroke of luck, then, that at our most vulnerable, we would naturally produce a chemical that floats up the nose of our partner and brings down his temperature. Sobel’s findings have implications that extend past the question of sexual appetite. Arousal encompasses both sex and aggression—a revved up appetitive stance toward the world that might be calmed by the sight of tears.

The question of why we weep has fascinated scientists. In the past, researchers offered up wide-ranging theories as to what crying's purpose could be. The biochemist William Frey discovered that tears brought on by strong emotion are different than those that result from an irritation to the eye, containing, among other things, higher amounts of the hormone prolactin. Women have more prolactin than men and cry approximately four times more often. Frey also argued that tears are the body’s way of expelling toxins from the body (which could explain why we feel better after crying). What Frey termed "emotional tears" also contain an endorphin called enkephalin, which has an anesthesitizing effect, giving way to the belief that crying might be a painkiller. Evolutionary psychology has weighed in as well, puzzling over the question of what is it about crying that would have been advantageous for survival. One interesting answer: In a more primitive era, tears, because they blur our vision, might have assured others that we were not preparing to attack, and thus promoted a more friendly reception. And tears garner effusive demonstrations of love and comfort—at least, that’s often the hope.

Of course, there’s much to be elaborated on here. How would these men have responded if the photographs they were given to look at were of their romantic partners? Perhaps tears drove down men’s attraction to strangers, but would foster the opposite effect toward women they were intimately involved with.

In the meantime, Sobel’s findings bring new meaning to what many girlfriends and wives already know: The power of tears should not be underestimated.

Casey Schwartz is a graduate of Brown University and has a master's in psychodynamic neuroscience from University College London. She has previously written for The New York Sun and ABC News. Currently, she's working on a book about the brain world.