The Science Of Crying

November 9th 2015

Out of all the species in the animal kingdom, we humans are the only species that actually shed tears in response to emotions (though potentially elephants and gorillas do as well). Other mammals and salt water crocodiles shed what are known as reflex tears to lubricate and protect eyes. 

But why do humans shed emotional tears?

Many scientists believe the theory that crying is a highly evolved behavior that developed in humans as a way to build relationships and strategically reduce conflict with others.

The evolutionary reason we cry.

According to evolutionary biologist Oren Hasson, crying compromises one of your most valuable assets as an animal: sight. (Water fills the tear ducts and your vision is impaired.) By putting yourself at this disadvantage, others perceive you as less of a threat.

“By blurring vision, tears lower defenses and reliably function as signals of submission, a cry for help,” Hasson said in an interview with Live Science. “You can show that you are submissive to an attacker and therefore potentially elicit mercy from an enemy, or you can attract sympathy from others and perhaps gain strategic assistance.”


The more that a species is able to identify pain and support each other, the more likely that species is to survive.

Being able to understand the mental state of others is fundamental in building and preserving relationships in complex societies, National Public Radio reports. If you are able to interpret the level of someone's pain then you are able to help that person. By crying, people are able to signal help from others.

The healing power of tears—physical and emotional.

An article from the Atlantic, the writer examines the book "Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond," which was written by Robert R. Provine, a professor of psychology and neuroscience. In the book Professor Provine examines the reasons why humans cry, and just one of the reasons he suggests is that tears may have some healing qualities for the eyes. He writes in his book:

"Non-emotional, healing tears may have originally signaled trauma to the eyes, eliciting caregiving by tribe members or inhibiting physical aggression by adversaries. This primal signal may have later evolved through ritualization to become a sign of emotional as well as physical distress. In this evolutionary scenario, the visual and possibly chemical signals of emotional tears may be secondary consequences of lacrimal secretions that originally evolved in the service of ocular maintenance and healing."

Dr. Judith Orloff also writes in Psychology Today about the healing power of tears—both physical and emotional.

"Our bodies produce three kinds of tears: reflex, continuous, and emotional," Dr. Orloff writes. "Each kind has different healing roles. For instance, reflex tears allow your eyes to clear out noxious particles when they’re irritated by smoke or exhaust. The second kind, continuous tears, are produced regularly to keep our eyes lubricated—these contain a chemical called 'lysozyme' which functions as an anti-bacterial and protects our eyes from infection."

"Tears also travel to the nose through the tear duct to keep the nose moist and bacteria free," Orloff continues. "Typically, after crying, our breathing, and heart rate decrease, and we enter into a calmer biological and emotional state."

Orloff also contends that crying does more than just physically heal the eyes, she argues that crying "helps to emotionally clear sadness and stress."

Although the evolutionary reason behind crying is a benefit, most cultures and many men refrain from doing so.

Share your opinion

Do you feel comfortable crying in front of others?

Yes 29%No 71%