Tue, 5 Feb, 2019
Can science explain why we cry?
There’s a lot scientists don’t know – or can’t agree on – about people who cry. Charles Darwin once declared emotional tears “purposeless”, and nearly 150 years later, emotional crying remains one of the human body’s more confounding mysteries. Though some other species shed tears reflexively as a result of pain or irritation, humans are the only creatures whose tears can be triggered by their feelings. But why?
Researchers have generally focused their attention more on emotions than on physiological processes that appear to be their by-products. “Scientists are not interested in the butterflies in our stomach, but in love,” writes Ad Vingerhoets, a professor at Tilburg University in the Netherlands and the world’s foremost expert on crying, in his book Why Only Humans Weep.
But crying is more than a symptom of sadness, as Vingerhoets and others are showing. It’s triggered by a range of feelings – from empathy and surprise to anger and grief – and unlike those butterflies that flap around invisibly when we’re in love, tears are a signal that others can see. That insight is central to the newest thinking about the science of crying.
For centuries, people thought tears originated in the heart. A prevailing theory in the 1600s held that emotions – especially love – heated the heart, which generated water vapour in order to cool itself down. The heart vapour would then rise to the head, condense near the eyes and escape as tears. Finally, in 1662, a Danish scientist named Niels Stensen discovered that the lacrimal gland was the proper origin point of tears. That’s when scientists began to unpack what possible evolutionary benefit could be conferred by fluid that springs from the eye. Stensen’s theory: tears were simply a way to keep the eye moist.
In his book, Vingerhoets lists eight competing theories. Some are flat-out ridiculous, like the 1960s view that humans evolved from aquatic apes and tears helped us live in salt water. Other theories persist despite lack of proof, like the idea popularised by biochemist William Frey in 1985 that crying removes toxic substances from the body that build up during times of stress.
Evidence is mounting in support of some new, more plausible theories. One such theory is that tears trigger social bonding and human connection. We cry from a very early age in order to bring about a connection with others. Humans come into the world physically unequipped to deal with anything on their own. Even though we get more capable, grown-ups never quite grow out of the occasional bout of helplessness.
“Crying signals to yourself and other people that there’s some important problem that is at least temporarily beyond your ability to cope,” says Jonathan Rottenberg, an emotion researcher and professor of psychology at the University of South Florida.
New research is also showing that tears appear to elicit a response in other people that mere distress does not. In a study published in February 2016, researchers found that tears activate compassion. When test subjects were shown a photograph of someone visibly crying, compared with the same photo with the tears digitally removed, they were much more likely to want to reach out and reported feeling more connected to that person.
Scientists have found some evidence that emotional tears are chemically different from the ones people shed while chopping onions. In addition to the enzymes, lipids, metabolites and electrolytes that make up any tears, emotional tears contain more protein. One hypothesis is that this higher protein content makes emotional tears more viscous, so they stick to the skin more strongly and run down the face more slowly, making them more likely to be seen by others.
Tears show others that we’re vulnerable, and vulnerability is critical to human connection. “The same neuronal areas of the brain are activated by seeing someone emotionally aroused as being emotionally aroused oneself,” says Michael Trimble, a behavioural neurologist at University College London. “There must have been some point in time, evolutionarily, when the tear became something that automatically set off empathy and compassion in another.”
A less heartwarming theory focuses on crying’s ability to manipulate others. Researchers believe that just as babies use tears as a tool for getting what they need, so do adults – whether they’re aware of it or not. “We learn early on that … crying can neutralise anger very powerfully,” says Rottenberg, which is part of the reason he thinks tears are so integral to fights between lovers – particularly when someone feels guilty and wants the other person’s forgiveness.
A small study in the journal Science that was widely cited – and widely hyped by the media – suggested that tears from women contained a substance that inhibited the sexual arousal of men. When 24 men sniffed real tears, they felt less aroused by photos of women’s faces, and when another 50 men sniffed them, they had measurably reduced testosterone levels in their saliva than they did when they sniffed the control saline.
The bigger story, believes Noam Sobel, one of the study’s authors and a professor of neurobiology at the Weizmann Institute of Science in Israel, is that tears might be reducing aggression, which the study didn’t look at. Men’s tears may well have the same effect. Sobel and his research group are currently wading through the 160-plus molecules in tears to see if there’s one responsible.
But what does all of this mean? It is a question researchers are now turning to.
Michael Trimble, one of the world’s leading experts on crying, says, “We don’t know anything about people who don’t cry.”
So, the question arises, if tears are so important for human bonding, are people who never cry perhaps less socially connected? That’s exactly what preliminary research is finding, according to clinical psychologist Cord Benecke, a professor at the University of Kassel in Germany. He conducted intimate, therapy-style interviews with 120 individuals and looked to see if people who didn’t cry were different from those who did. He found that they were. “The non-crying people had a tendency to withdraw and described their relationship experiences as less connected,” he says.
Tearless people also experienced more negative aggressive feelings, such as rage, anger and disgust, than people who cried. More research is needed to determine whether people who don’t cry really are different from the rest of us, and some is soon to come: Trimble is now conducting the first scientific study of people with such a tendency.
So far, though crying appears to have interpersonal benefits, it’s not necessarily unhealthy not to do it. Virtually no evidence exists that crying comes with any positive effects on health. Yet the myth persists that it’s an emotional and physical detox, “like it’s some kind of workout for your body,” Rottenberg says. One analysis looked at articles about crying in the media – 140 years’ worth – and found that 94 per cent described it as good for the mind and body and said holding back tears would result in the opposite. “It’s kind of a fable,” says Rottenberg.
Also overblown is the idea that crying is always followed by relief. When researchers show people a sad movie in a laboratory and then measure their mood immediately afterwards, those who cry are in worse moods than those who don’t.
But other evidence does back the notion of the so-called good cry that leads to catharsis. One of the most important factors, it seems, is giving the positive effects of crying – the release – enough time to sink in.
When Ad Vingerhoets and his colleagues showed people a tearjerker and measured their mood 90 minutes later instead of right after the movie, people who had cried reported being in a better mood than they had been before the film. Once the benefits of crying set in, he explains, it can be an effective way to recover from a strong bout of emotion.
Modern crying research is still in its infancy, but the mysteries of tears – and the recent evidence that they’re far more important than scientists once believed – drive Vingerhoets and the small cadre of tear researchers to keep at it.
“Tears are of extreme relevance for human nature,” says Vingerhoets. “We cry because we need other people. So Darwin,” he says with a laugh, “was totally wrong.”
From ‘Why We Cry’ in Time, July 2016 © 2016 by Mandy Oaklander. Published by Time Inc.