The Science of Tears

(Detail from ‘The Descent from the Cross’ by van der Weyden)

From a young age, we’re told not to cry. That’s what babies do. Adults aren’t meant to weep and wail. And yet: we all do it. Be it a break-up, the loss of a loved one, or the season finale of Game of Thrones. Sometimes the sheer weight of emotion brings us to such a point that the only way to cope is to shed a few tears. But why do we do this? Scientists through the ages have sought to understand the purpose behind humanity’s need to cry and much has been discovered. Yet even today, there is still much we don’t know, leaving our understanding of tears as enigmatic as ever.

What we do know is this: there are three distinct types of tears. The simplest type of tear is known as the basal tear. These tears exist to keep your eyes moist and functioning. Then there are the reflex tears. These are the tears that your nervous system (or if you want to be a really precise know-it-all about it, your “ophthalmic nerve”) creates when foreign particles irritate the eye. These are the type of pesky tears that one gets when chopping onions or when getting pepper sprayed in the face for being a weirdo.

The third type of tear is the most mysterious: the psychic tear (also known as the emotional tear). These are the tears one has when overcome with emotion: grief, pleasure, pain. Remember that time you came home and found that your flatmate had eaten all of your delicious leftover Chinese food? The tears you cried then were psychic tears. These tears have a distinct physical make-up from the other kinds, containing more protein-based hormones. Unlike basal and reflex tears, however, scientists struggle to explain the purpose and function of psychic tears. An eye must lubricate itself and create tears to rid itself of irritant vapours but why does the body react in such a way to one’s emotions?

The above question has been at the center of the scientific debate surrounding tears for over a century. Charles Darwin’s opinion of emotional tears was that they were “purposeless.” Others have taken a different view. The leading theory, as outlined in Ad Vingerhoets’s book Why Only Humans Weep, is that crying is a form of communicating one’s need for help. It’s certainly true for babies. When first born an infant can only communicate to his parents by crying. Yet why does crying continue into adulthood? An infant will stop breastfeeding as it gets older. So why do we still continue to cry emotionally as we age? While fully functioning adults don’t tear up because they need to use the loo, they will cry when they are in emotional stress. Crying, then, is a way of communicating one’s emotions in a way that can’t be expressed in words.

A more cynical theory focuses on the manipulative powers of tears. This idea has evolved out of an ancient Greek idea of “crocodile tears”; tears meant to trick prey into thinking they are harmless until they are close enough to snap up in their long jaws. Nevertheless, tears send a very strong response to other humans: they can diminish anger and bring people together. Either way—whether tears are seen as a manipulative survival mechanism or just as a signal for help—both theories posit the same notion: that crying is a form of communication.

But what about when we cry out of joy? What the heck is that about!? Yale psychology Professor Oriana Aragón wrote a paper on the subject of illogical emotional reactions. Aragón suggests that sad smiles, nervous laughter and tears of happiness are forms of “emotional regulation.” One laughs nervously to put their nervous feelings in check. One cries out of joy so that they’re not overwhelmed by happiness. You can cite this article the next time you inappropriately laugh at someone’s terrible news. You’re emotionally self-regulating yourself.

Tears, then, play a crucial role in our lives. They are not something that should be repressed and scoffed off as something childish. They serve an important purpose of regulating one’s emotional health as well as communicating to others when you need comfort and aid. And don’t forget that without the basic basal tears your eyes would simply dry out and leave empty horrible sockets in your face. Now that would be something to cry about.