Why Do We Cry Sad Tears?

Hey smart people, Joe here. How are you feeling today? How are these definitely-not-generic-stock
photo people feeling? Are they neutral, ashamed, stoically handsome? Sometimes it can be a little hard
to tell. But if we add a few tears to these facial
expressions, voila – these people look super sad. When we see faces get all contorted and messed
up and liquid leaking out of eyeballs, that sends a clear, unambiguous emotional message. Because we are the only animal that cries. Why? [OPEN] Pain. Sorrow. Dangerous foreign objects. All of these things can make people cry. This reaction makes sense when say, dust,
gets into your eye, which always seems to happen when I watch the beginning of Up. [sigh pause thought bubble scene] You make
tears to flush your eye clean. But what’s the point of making tears when
we’re sad? Why did humans evolve emotional crying? We make a few kinds of tears. Tears of sadness are called emotional or psychic
tears. They differ from reflex tears, which we make
to flush our eyes in response to irritants. We even make a third type of tear, basal tears:
a liquid force-field we’re constantly producing to protect and lubricate our eyes. Each tear type has a different recipe. All three contain salt, proteins, and antibacterial
enzymes, but emotional tears have higher amounts of protein, including stress hormones and
natural painkillers that we don’t yet know the purpose of. And while all three are secreted from the
lacrimal glands in your eye, only the production of emotional tears is controlled by the hypothalamus
– an area of your brain that regulates emotional responses. Across cultures, aside from speaking, humans
communicate with each other in many ways: through gestures, posture, even touch. But we tend to read other people’s emotions
through their face. We have over 40 muscles in our face alone,
capable of deforming our appearance in a number of very weird ways. Like blushing, laughing, and teenage eye-rolling,
before we had language, it’s possible tears evolved as a way to send a message to people
close to us that we were experiencing strong emotions. Individuals that could clearly and reliably
communicate sadness were more likely to receive help, which increased the likelihood they
would survive and reproduce. We can’t know for sure, but it makes evolutionary
sense. And so do crying babies. A baby can’t tell you that they’re hungry,
tired, or uncomfortable, because they can’t talk, so tears are effective baby communication. But humans keep crying into adulthood. Adults don’t cry with as much noise as babies
do, THANKFULLY… can you imagine? But our grown up eyes still shed tears. Studies show that most people that see tears,
want to help. That’s because, while evolving tears, we
also evolved a response to them: feelings of empathy or sympathy. We tend to see a crying person as helpless
and feel more connected to them. These feelings likely helped us develop social
bonds. That innate response is why you probably felt
different when we added tears to these pictures. Lots of animals make tears, but as far as
we know, we’re the only animals to cry emotional tears. Other animals have distinct facial expressions
to communicate fear or pain, but no other species that we know of has a sad signal quite
like tears. It’s true we also cry at happy things, and
scientists don’t exactly know why. Perhaps we’re just plain overwhelmed with
emotions. Or it could be that you’re actually crying
at the sad part of the thing, like how weddings and graduations signify the end of something,
or when you’re happy to see someone because you missed them so much. There’s a lot we still don’t know about
crying, but it’s clear that it’s one of the most human things we do. Why didn’t they get one more adventure together. Stay Curious.