The Science of Tears: Why Do Humans Cry?

Crying depends on your culture, gender, attachment style, and so many other factors.

My mom, sisters, and many female friends are addicted to the show This is Us. When it’s about to air one of them usually posts something to their social media like, “Better get the tissues ready.” Of course, I myself avoid the show like a plague ravaged raccoon. But it got me thinking about this sadness-induced physical response. We can cry out of sadness, fear, frustration, anger, or even joy. But why do streams of liquid leave our eyes?

The truth is no one really knows for sure. That is to say, scientists don’t agree why tears stream down our cheeks and we’re wracked with spasms, and of course the telltale wailing and sobbing that comprise having a full-blown cry. There’s also great variety among humans. We all have a different threshold for the act. Some of us never even cry at all.

In a scientific sense, we’re the only organisms who tear up due to our emotions. Other creatures do so merely to remove irritants from their eyes. Many psychologists believe that in addition to giving us an outlet for a rapid buildup of a powerful emotions, crying is a social signal to others that we’re in distress. Care-taking at times of great stress can increase the bonds between individuals in a group, making them more in tune with one another, better able to communicate and understand each other, increasing teamwork among them and so their likelihood of survival.

Crying may be a social cue for support, which can in turn lead to more social cohesion. Getty Images.

Children and infants cry to get the attention of parents and have their needs met. Biochemist William H. Frey, PhD in the 1980s studied crying and tears. He found that on average, women cry 5.3 times a month, while men cry 1.3 times in that same time period.  

There may be a biological reason behind this. The hormone prolactin is thought to promote crying. This is found at higher levels in women. While testosterone may dampen the act. Crying is different in different cultures as well.

In a 2011 study published in the journal Cross-Cultural Research, investigators looked at 35 different countries to see how often women cried. Richer countries such as the US, Sweden, and Chile saw slightly higher rates of female crying, over poorer ones such as Nepal, Ghana, and Nigeria. Researchers believe it’s because there’s greater freedom of expression in developed countries.

One’s attachment style also plays a role. Dismissive attachment styles, those people who avoid or distrust intimacy, are the most likely to try not to cry, or fight back tears. Those with insecure attachment, the needy, may cry inappropriately, such as going into histrionics in order to receive attention. While those with secure attachment style are the most likely to cry appropriately and naturally.

Women cry more often than men, and women from richer countries more often than poorer ones. Getty Images.

Some studies have looked into how children and others use tears as a form of manipulation. A child may cry in the presence of an angry mother to induce sympathy and try to get out of trouble. This could also be one reason why crying is often part of lovers' spats. A small study found that female tears can actually lower male sex drive and temper male aggression.

Another interesting find is that tears formed from different emotions actually contain different chemical makeups. Emotional tears contain more protein which is thought to make them thicker and so more likely to slip down slowly, causing streaks down the cheeks, which are easily noticed by others. It’s a call for support and empathy. Along those same lines, artist Rose-Lynn Fisher took tears shed from different emotions and photographed them under a microscope. The results are fascinating though not wholly scientific. 

Meanwhile, scientists are turning their lenses on to those who don’t cry. Though we’re often think a good cry is a healthy catharsis, there’s actually no evidence to back this up. Some psychologists however, believe that bottling up such emotions might lead to feelings of anger later on while some scientists see crying as a way to shed the hormone cortisol from the body, ejecting it with the tears themselves.

To learn more about the science behind crying, watch this: 

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