Yawning is something you likely do every day, but oddly enough, scientists still aren't sure why.
Recently, the scientific community has moved toward the idea that yawning is a thermoregulatory behavior that cools down the brain, but its true biological function is still unclear.
What's more, scientists aren't entirely sure why it's contagious among social animals like humans. A 2005 study published in Cognitive Brain Research found that the
networks in your brain responsible for empathy and social skills are activated when you see someone yawn. Researchers have also observed that chimpanzees can "catch" yawns from humans.
"Copying the facial expressions of others helps us to adopt and understand their current state," said Dr. Matthew Campbell of Yerkes National Primate Research Centre at Emory University.
This is why, according to one study, psychopaths aren't as susceptible to contagious yawning.
Read more: Catching someone's yawn is linked to empathy, and psychopaths are often immune