Of all human behaviors, crying is one of the most unique and curious. In fact, emotional crying is the only physiological function that is exclusive to humans. We cry when we are sad, hurt, tired, frustrated, angry . . . but to what end? Why do we cry?
Three Types of Tears
As humans, not only are we unique in crying, we also shed three different types of tears, which are chemically different from each other.
Basal tears: These tears are always present, and are used to lubricate, nourish, and protect our eyes. Basal tears are necessary for clear vision and ocular health, as they keep the surface of the eye smooth and clear to help reduce risk of infection. These tears are made up of oil, water, and mucus. The outermost layer of oil helps prevent evaporation of the second layer of water, while the third layer of mucus helps evenly spread tears across the surface of the cornea. Our bodies produce five to ten ounces of basal tears every day. Click here to learn more about basal tears and how they help keep eyes healthy and nourished.
Reflex tears: These tears appear in response to irritants such as smoke, wind, and chemicals (like the one that makes us tear up when chopping onions!). These are released in large quantities to wash away substances the eye perceives as harmful; the aqueous layer of these tears also contains antibodies to kill microorganisms. Reflex tears have been found to be about 98% water.
Emotional tears: These are the most mysterious tears, as scientists are unsure why, exactly, we cry as an emotional response. In the time of Hippocrates, it was thought that tears were triggered by the mind; Charles Darwin once called emotional tears “purposeless.” While there is not yet a proven reason for emotional tears, there are many theories as to why we cry when experiencing strong emotions.
Theories Behind Emotional Tears
One theory suggests that emotional crying is a way to elicit compassion, while another states that emotional tears developed as a way to signal others to vulnerability silently so as to not alert predators to weakness. There is also a theory that suggests that tears and crying help build relationships and even communities by eliciting the empathy of those around us.
Emotional tears are curious because humans are the only creatures whose tears are triggered by feelings. Though we know that babies cry in order to gain attention and care from adults, there is no hard evidence as to why adults cry. It’s particularly confusing, in fact, because of why adults cry – tears can be triggered by a range of feelings from sadness to surprise, from anger to happiness, from grief to empathy.
Chemicals of emotional tears may give us some clues as to their purpose. Along with the correlation to an emotional response, these tears are characterized by:
- The presence of enkephalin, an endorphin and natural painkiller that helps to boost mood.
- High levels of the stress hormone ACTH, which causes the release of hormones like cortisol.
The presence of these chemicals is interesting. Cortisol supports our “fight or flight” response by increasing blood sugar and blood pressure, so this release via tears readies the body to perform physical activity as a response to tears. This is what allows some people to perform extraordinary feats in emergencies, such as lifting a car when someone is trapped underneath. Alternately, it is thought that crying may actually be a response to high levels of ACTH; as stress builds internally via cortisol but isn’t relieved through physical activity, we may feel overwhelmed and even experience physical symptoms like hyperventilation or heart palpitations. Getting rid of ACTH through tears can help alleviate these feelings.
Because the chemicals present in emotional tears work to stabilize moods, emotional tears are also thought to be a simple release of physical stress. In studies, people who cried after watching a sad movie were in a better mood after their cry than they were before they had seen the film. It appears that once the chemical benefits of crying set in, the results can be a good way to rebalance after a bout of strong emotion.
While the research of emotional tears is still limited, they are being recognized as a positive representation of us as humans. We may not know the reasons our emotions elicit tears, but we do know that emotional tears show how connected we are with our world. We also know that tears are scientifically proven to make you feel better. If you are concerned that you get tearful too quickly and too often, be sure to talk with your doctor. If you have other concerns or questions about your eye health, contact us.