Yawning is something you probably do every day, but scientists are still not sure why.
More recently, the scientific community has subscribed to the idea that yawning is a thermoregulatory behavior that cools the brain, but its true biological function is still unclear.
Scientists also do not know exactly why it is contagious among social animals like humans. A study published in Cognitive Brain Research in 2005 found that the networks responsible for empathy and social skills in your brain are activated when you see someone yawning. Researchers have also observed that chimpanzees can "catch" people's yawning.
"Copying the facial expressions of others helps us to take over and understand their present state," Dr. Matthew Campbell from the Yerkes National Primate Research Center at Emory University.
For this reason, psychopaths are not as susceptible to contagious yawning, according to a study.
Read More: Yawning of someone is related to empathy and psychopaths are often immune