Subtitles section Play video Print subtitles - The first thing you did in this world was cry. What does it say about the human condition that when you enter this world crying, the doctor's like, the baby's emotionally devastated to be here, check. Humans are the only animals that produce tears due to emotion. Elephants, for example, produce tears, but mostly due to irritation. In fact, the lobocraspis griseifusa moth will irritate an elephant's eye so it produces tears that it can drink. Imagine asking a kid what their favorite animal was and they were like, Oh you know, the moth that irritates elephant's eyes in order to drink their tears. I'd be like, okay, this kid, he's got issues. You on the other hand could produce tears from a loss, joy, self-pity, laughter or when the tone switches in a "That's So Raven" episode. And tis wild, but the chemical makeup of your tears changes based on your emotions. So why are human tears so unique? Tears of endogenous depression are different than tears from acute grief. If you remove the tears from crying people's faces, it's hard for you to tell if they're crying from sadness or laughing from pure joy. Scientists have a hard time studying tears, especially emotional ones. A lot of these studies involve humans as lab rats, watching sad movies and studying their crying behavior. Or there are morbid studies. For example, the one on brain dead people, where they found they produce tears when their organs are removed and will slightly open their eyes when their nipple is twisted. For this next study, could you twist that brain dead person's nipple, please? (laughing) Do not kill the messenger. I did not twist those nipples a scientist did. Oh, they opened their eyes slightly, fascinating. Due to recent scientific insight we know a lot more about why we emotionally cry. Back in 17th century America for example, it was thought that a marriage was doomed if the bride did not profusely weep at the wedding. This was to prove the bride wasn't a witch, as witches were known to cry only three tears from the left eye. Therefore obviously the bride was crying from both eyes it meant that the bride was not working with Satan. Think of all the groomzillas who were like, she's ruining my perfect day, she's not crying from both eyes. Thine is a witch honestly straight weddings are like, so over the top. To know why you as a human cry, you have to think back millions of years to when your ancestors evolved out of the water. Yep. Your great, great, great times a million million grandparent looked like some sort of insect-y shell amphibian arthropod millipede sort of thing, maybe. And by leaving the water to live on land, all of these land dwelling animals from then on needed a lacrimal apparatus to produce tears that kept the eyes wet while on land. But you, my friend are special because you have three types of tears. The first is basal tears, which is made up of three layers. A mucus layer that touches the eyeball, an aqueous layer, which moisturizes and protects against invasive bacteria, and the final oily layer that stops the other layers from evaporating and keeps the surface of the eyes smooth. So your vision is clear. The second is reflex tears, which is unique to all land dwelling animals. In fact, all animals, except for snakes and amphibians, have a peripheral sensory system that consists of nerve endings in the eye that when stimulated by mechanical, thermal, chemical, or pain stimulus release tears. It should be known that you don't have a storage of tears in your eye, ready to come out when you cry, the tears are created due to a sensory in your body that triggers the response. Humans, that means me, that means you are special. We are the only animals with emotional tears, also known as psychogenic tears. Which are controlled by the prefrontal cortex and the anterior portion of the limbic lobe of the brain. Some scientists think that we cry because as a child, crying was the only way that we were able to get a response from our parents. As babies, we don't have the words to express our feelings, so crying is what we do, and it works. Known as the acoustic umbilical cord. Crying serves to connect the infant to the caregiver as an adaptive strategy. Developmental psychologists believe that crying enhances infant survival by eliciting care and protection from caregivers. In lactating, females infant crying can cause a rise in breast temperature and a milk let down reflex. But the crying starts to decrease at a time of for brain development in the baby. When the baby is 24 months old concurrent with rapid development of spoken language, crying seems to fall off. Because of this research, some scientists posit that we cry when we don't have the words to explain how we're feeling. Which I can relate to. I feel like when I cry, it's usually in moments where I don't have the words to express what I'm feeling. Much like when I was a kid, crying for my mom's attention, when I couldn't speak English. It feels like now when I cry it's when emotions are so big I don't really know how to explain them. Whether they're happy or sad. And crying, it's showstopping. If you cry at a party, people are going to pay attention to you. I have a hard time when the attention is on me in public settings, so I really like to cry alone while watching a movie. In fact, once my mom almost kicked me out of a movie theater because I was crying so loud during "Ever After" that the people in the audience were like, please be quiet. We can't even focus on the movie. Emotional tears are really cool. But it turns out that the chemical makeup of tears from emotion are different than the tears from irritation. A study found that the protein concentration of emotional tears was 24% greater than that of an irritant, and the higher protein tears fall more slowly on the face. Some scientists think that emotional tears evolve to have more proteins in them causing them to fall slower and give more time for our fellow humans to react to the response and give us an emotional boost. In fact, using eye tracking, a new study found that humans focus way more on faces with tears and are more aroused by them. The visual image of a tear falling down a cheek sets off a response in us to help and be interested. This all leads to the predictions that human emotional crying is a way to get other people to look at you. The higher protein concentration of emotional tears makes them fall more slowly, so people will pay attention and look after you. There is no gender difference in crying frequency in infants, but there is a big shift when we get to adulthood. In a sample of 286 women and 45 men between the ages of 18 to 75, it was found an average of 5.3 crying episodes per month for the women. And 1.4 crying episodes per month for the men. For the women, most of the cries had to do with a sad film or TV show. In fact, studies show that from 11 to 16 years of age, boys cry more from physical pain. Whereas girls cry more for empathetic reasons, especially during movies again, or TV shows. This led some other studies to posit that women are more empathetic to the crying of others and found they're more likely to stop and help someone crying on the street.