Crying over spilled milk and other interesting facts about our tears

It’s only human to cry. Well, kind of. While other animals shed tears as a means to lubricate their eyes, (yes, crocodiles tears are real) emotional crying is exclusive to humans.

Types of tears

There are three main classifications for tears. Our basal tears are on duty around the clock, and form the protective tear film which constantly lubricates the surface of the eye. Protecting us from irritants such as smoke and onions are our reflex tears.

However, it is our emotional tears, unique to the human experience, which have been attracting all the attention lately. Like the unique composition of a snowflake, the variable chemical composition of each tear may perhaps carry greater meaning, and serves as a topic in increased interest for researchers today.

Photographer Rose-Lynn Fisher captured the intricate nature of tears in stunning detail through her project, the Topography of Tears.

Why are you crying?

calamity_photography / Flickr
calamity_photography / Flickr

Scientists don’t quite know exactly why we cry. Though there may not be a comprehensive answer, they have proposed many plausible theories.

From an evolutionary perspective, scientists propose that humans cried to signal distress without making noise. With a predator nearby, any sound could reveal an otherwise covert location.

Lauren Bylsma, a post doctoral scholar at the University of Pittsburgh, further elucidates that humans cry “to elicit support from others during times of distress.” Whether an infant or grown adult, our tears signal to others a need to be comforted.

Finally, Jesse Bering of the Institute of Cognition and Culture at Belfast University suggests our tears can expedite conflict resolution by eliciting compassion and guilt. He told NPR, “It’s hard to punish somebody or argue with someone who’s crying … It’s like a trigger that tells us to back off.”

All wired up for the waterworks

Whether happy or sad, scientists agree that both categories of emotional tears “have in common a period of intense emotional arousal.” Mark Fenske, Ph.D., associate professor in neuroscience at the University of Guelph explains, “Indeed, brain regions associated with emotional arousal, including areas of the hypothalamus and basal ganglia, are connected to a section of the brainstem called the lacrimal nucleus that stimulates tear production.”

Crying “like a girl”

Yes, women do cry more than men. Women average 5.3 cries per month, versus 1.4 times per month for men. Women also cry for longer periods of time averaging 6 minutes, which is 2-3 times longer than the average male.

Dr. Geoffrey Goodfellow highlights, “That men have larger tear ducts in their eyes, so that it is less likely for the tears to well up to the point of spilling over the eyelid onto the cheek.”

By the time women reach 18, they have 50% to 60% higher levels of prolactin in their bloodstream than men do. The prolactin hormone is a lactation catalyst which aids in tear production. Biochemist and neuroscientist Dr. Frey states,”We believe this is one of the reasons that women cry more easily.”

However, as men age and their testosterone levels decrease, they also cry more. This can be provoked by altruism, camaraderie and issues of morality.

What about chopping onions?

You find yourself tearing up when chopping onions because of an irritant called syn-propanethial-S-oxide, which all onions release. Syn-propanethial-S-oxide stimulates the lacrimal gland and thus creates what are known as reflex tears.

My Dog Skip and the Titanic

Admit it. You cried like a baby. But why do movies make us cry? Neuroeconomist Paul J. Zak attributes this phenomenon to the neuropeptide oxytocin: “The hormone oxytocin engages brain circuits that make us care about others, even complete strangers. Perhaps surprisingly, oxytocin engages at the smallest suggestion that someone wants to connect to us.”

Go for it. We all need a good cry every once in a while.