The shedding of tears due to emotions is unique to humans. In the past, researchers suggested that crying helps carry stressful chemicals away from the body, or that it lets babies signal health problems.
But when tears blur vision, they can readily handicap aggressive behavior. As such, tears signal vulnerability, a strategy that can emotionally bind others closer to you. The use of tears could be to build and strengthen personal relationships.
According to many scientists, crying is an evolved behavior exclusive to humans, but no one truly knows exactly why we developed the capacity to cry.
Crying as a Means of Strengthening Bonds
According to evolutionary biologist and lead researcher Oren Hasson:
"My analysis suggests that by blurring vision, tears lower defenses and reliably function as signals of submission, a cry for help, and even in a mutual display of attachment and as a group display of cohesion."
As such, tearing up or crying can be “used” to build and strengthen personal relationships, and if you cry when seeing someone else cry, it can signal your compassion or empathy.
You may also potentially attract sympathy and help from others, or mercy from an attacker – all of which could increase your chances of survival.
And, although crying in public is usually frowned upon, tears tend to make us believe that whatever the person crying is saying or doing is more authentic.
Crying is a Form of Communication
Cellular physiologist Darlene Dartt’s research shows that your nervous system may be responsible for crying.
When nerves near your tear gland release certain neurotransmitters (chemical messengers) and hormones (such as pituitary hormones), tears are triggered.
According to Dartt, crying began as an involuntary protective response mechanism, also referred to as “reflex tears.” Your cornea contains sensory nerves that operate just like the pain nerves in your skin. So when dust or debris gets in your eye, or when you’re slicing an onion, for example, the nerves in your eye send impulses to your brain stem, which releases hormones that instruct your tear glands to produce tears to wash away the irritant.
But there are also nerves in the cornea that reach further up in your brain, into an area of your cerebrum that processes emotions, and “emotional tears.”
When an emotion is registered in your cerebrum, such as ecstatic joy or sorrow, it sends a signal to your endocrine system to release hormones that generate tears.
Your cerebrum also controls speech, and just like speaking, crying is a powerful form of communication, and one of our main forms of human communication during the first several months of life.
The main difference is that whereas you can consciously decide what to say and how to say it (and it may be emotional in nature or not), crying is a form of communication that is entirely emotional – a more or less uncensored communication of how you really feel about something.
Why Do Women Cry More Than Men?
On average, women cry about 64 times a year, compared to 17 crying episodes for men.
Some have speculated that the reason why women cry more than men has to do with the differences found in men’s and women’s brains, but no one has been able to prove this to be the case.
Researchers have found that as children, boys and girls cry equally often, but once they enter school, boys cry less and less. This suggests there’s likely a societal root to these differences; parents and peers tend to come down heavier on boys who cry as they grow up.
This could be due to an evolutionary adaptation, according to Randy Cornelius, Ph.D., a psychology professor at Vassar College and one of only a few dozen researchers, world-wide, who study crying.
Crying signals that you’re vulnerable and in need. Women tend to share their emotions (and tears) as a sign of trust, which increases bonding and chances of survival. From an evolutionary perspective, a male hunter and protector who cries would be sending the wrong signal and may reduce his chances of survival.
Another researcher in the field of crying, William Frey, Ph.D., biochemist and author of Crying: The Mystery of Tears, theorizes that women are more prone to tears due to hormonal variances between the sexes.
The hormone prolactin increases in women during puberty, menstruation, pregnancy, and breastfeeding. It also increases in both sexes during stress. Women average as much as 60 percent more prolactin than men. Frey believes this difference may lower a woman’s emotional bar and make her more prone to cry.
Interestingly though, around mid-life, the tables start to turn; women begin to cry less and get more assertive and can display anger more. As men age, they get angry less, and yes, cry more.
This phenomenon corresponds nicely with your hormonal levels.
As women age, their levels of female hormones decrease, leaving higher concentrations of testosterone, the male hormone. Likewise, men’s testosterone levels decline as they age, which makes the impact of their female hormones more pronounced.
Whatever the reason for crying, there’s no doubt it’s a powerful form of communication that can make you feel better, help release stress, deepen social bonds, and may even have other biological functions we have not yet discovered that help maintain a healthy equilibrium.