According to Dr. Meredith Williamson, a psychologist and clinical assistant professor at Texas A&M, scientists previously believed that yawning is an indication of a need for sleep. However, today, they think that it can communicate a shift in alertness to boredom. A yawn is a way for the body to get a fresh supply of oxygen. Yawning is commonly done by stressed people or athletes whenever they need to be alert. Although researchers still do not fully understand why yawns are contagious, they have come up with a few theories.
One well-known theory on why yawning is contagious is that it is associated with empathy. People who have greater levels of empathy are more likely to yawn more frequently when someone else yawns compared to someone who has lower empathy levels, or someone with a mental disorder. According to Williamson, research has shown that yawning may not be as contagious to people with autism or schizophrenia. A 2013 study found that when children with autism focused their gaze on people's mouths instead of their eyes, they were more likely to experience a contagious yawn. This suggested that facial expressions and social cues may be more of a factor than empathy.
Yawning is also not universal to all ages. Children below four years old, together with older adults, are less likely to yawn in response to somebody else. This is because yawning is influenced by multiple factors, such as social cues, empathy, and possibly other influences.
Another theory of why yawning seems contagious is because it may be an unspoken form of communication. However, it is not exclusive to humans, as some species of primates and canines tend to yawn in response to each others' yawns. In fact, dogs have shown evidence of their unique bond with humans by yawning after a person yawns.
“It's multifactorial,” Williamson said. “It could be partly an innate form of communication or it could be related to empathy or a bit of both combined with other factors.”
More studies are needed to fully understand why people yawn after hearing or seeing other people yawn. Next time you are in a room full of people who are tired, watch for one person to yawn and see how long it takes for yawning to spread throughout the room.
Further research discovered that yawns become more contagious the more a person is close to someone. In a 2011 study, it was found that yawns were more contagious between family members, followed by between friends, and least contagious between strangers. However, when yawns did spread among strangers, it took more time for that second yawn to start compared to when yawns spread among family and friends.
One of the reasons why people yawn is because the brain needs cooling. Yawning gives the brain some fresh air, and it cools it down. In turn, this would provide additional energy needed in times when we let out a big yawn. Since lack of sleep increases brain temperature, we may need extra yawns when we are sleepy for extra cooling power. Furthermore, a 2011 study found that people tend to yawn more during cooler months and less when the temperature is warmer.
Research also found that the bigger your yawn, the bigger your brain. In a study published in the journal Biology Letters, researchers found that mammals that let out big, long yawns had heavier brains with a greater number of brain cells. Other studies also suggested that yawning more than normal is associated with health conditions, such as a stoke or a tumor. (Related: Big yawns are a sign of having a large brain.)
Read more news stories and studies on how the body works by going to MindBodyScience.news.