Animals may “cry” by making sounds for emotional expression or pain, but humans are the only animal that actually sheds tears, which leads us to the question: why?
Scientifically speaking, tears are a result of action in the lacrimal gland situated between your eyeball and eyelid. When you blink, the fluid disperses over the eye, then drains via the lacrimal punctum (and your nose which is why crying often causes your nose to run). If tears are copious, this drainage system can be overwhelmed, and tears will flow down your face.
But all tears are not the same. Here are the three main types:
- Basal variety. These are produced to lubricate and protect the eyes. Such tears are continually secreted in very tiny amounts (about 1 gram every 24-hours) which coat your eyes as you blink.
- Reflex tears. Also for protection, these are released in response to irritants, like dust, smoke or cut onions.
- Psychic tears. These are the most enigmatic tears, manifesting in reaction to strong emotions – stress, joy, sadness, physical pain, fear, etc. The area in your brain that specifically deals with emotions (hypothalamus) is hard wired to your autonomic (involuntary) nervous system which controls the tear system. Thus, your emotional reaction can automatically trigger your nervous system to activate tear production.
Basal and reflex-type tears are logical adaptations to our environment. But is there some survival advantage to shedding psychic tears? Most theories suggest that tears, which lend the face an appearance of sadness, may be helpful in gaining support from the community in time of need. Because tears create a perception of vulnerability, of someone who is less of a threat, tearing up can enhance personal relationships, build empathy. It can arouse a sense of group cohesion in difficult circumstances.
Nature has included an added bonus to crying. Tears contain a high level of a chemical linked to stress – adrenocorticotropic hormone (ACTH). So, if you cry when you’re emotions are heightened, the body is releasing excess stress chemicals, leaving you feeling more relaxed. You feel better, more prepared to cope, after a good cry.
We human beings are an interesting, complicated bunch. Thankfully, we’ve got many tools at our disposal, including tears, to help us survive and thrive through the years.
Watch this short video which nicely sums up the situation:
“Why humans like to cry” – Scientific American
“Teary-eyed evolution: crying serves a purpose” – NPR
“How crying works” – HowStuffWorks.com