“A yawn is quite catching, you see. Like a cough.
It just takes one yawn to start other yawns off.”
— Dr. Seuss’s Sleep Book (1962)
We have all experienced it. A coworker stretches his arms above his head, opens his mouth wide and lets out a loud yawn. And suddenly, your body unconsciously starts to do the same. What makes a yawn so contagious? Let’s explore some of the science and theories behind this curious phenomenon.
We know we yawn when we’re tired, but why? This simple question does not yet have a simple answer. There are a handful of popular theories. One theory is that during periods of time when our vigilance decreases, a yawn may have an arousing affect. Another theory is that when we are relaxed, we are not breathing as deeply, and a yawn allows us to expand our lungs and keep them functioning at their optimum. More recent theories suggest that yawning may help cool the brain in situations when it gets too hot. No theory has been proven correct.
Even though the purpose of yawning is unknown, there are some common beliefs behind yawning that science has proven incorrect. You may think yawning only happens when bored or sleepy. Yet it is not uncommon to see Olympic athletes yawning just prior to their events. A study that looked at soldiers about to parachute out of an airplane for the first time showed an increase in yawning just prior to the jump. So it’s not just boredom or sleepiness that brings it on. Yawning may trigger the brain to make a change in its state, either from bored to alert, sleepy to awake, etc.
But none of these theories seem to explain the curious phenomenon of contagious yawning. Even simply thinking about yawning will often trigger one. You may have already yawned right now just reading about it. What makes a yawn so catching? This, too, is a mystery.
There are some surprising things we do know. Even though children begin yawning as early as their first trimester as fetuses, they don’t experience the contagious yawn until closer to 5 years of age, around the time they develop better social understanding and empathy. We are more likely to mimic the yawn of others when we know them well, a result that has been shown even in chimpanzees.
Given the tendency to mimic yawns from those that we are tied to socially, perhaps yawning serves a deeper role that is not yet recognized. It may help us better understand disorders that affect empathy and social reciprocity. For example, children with autism yawn just as often as other children, but are much less likely to have a contagious yawn.
Scientists have tried to unravel the mystery behind the contagious yawn by evaluating which areas in the brain light up when we see others yawn. One area that seems to be involved is the mirror neuron system, an area that is important for understanding actions and imitating them. However, many other areas of the brain also seem to be involved. The common link seems to be that the areas relate to social behavior and empathy.
The mysteries and debate behind the yawn will likely continue for quite some time. And you thought yawns just meant you were tired. Perhaps the yawn isn’t that boring after all.
About The Author
Sujay Kansagra, MD is the director of Duke University’s Pediatric Neurology Sleep Medicine Program and author of the book “My Child Won’t Sleep.” Dr. Kansagra offers Daily Doze readers tips and insight about the importance of sleep, especially for kids who need plenty of rest to grow and develop. Dr. Kansagra graduated from Duke University School of Medicine, where he also completed training as a pediatric neurologist. He did his fellowship in sleep medicine at the University of North Carolina in Chapel Hill, before joining the faculty at Duke as an assistant professor. He specializes in treating a variety of sleep disorders, including sleep apnea, insomnia, narcolepsy and parasomnias. He shares advice on sleep, medicine, and education through his Twitter accounts @PedsSleepDoc and @Medschooladvice. When he’s not busy at work or on social media, Dr. Kansagra enjoys spending time with his wife and two sons. And yes, they are both great sleepers.
Best Night’s Sleep: Not just a sleep expert, but also an expert sleeper, Dr. Kansagra can sleep almost anywhere, thanks to years of sleep deprivation during medical school and residency call nights. But his best sleep is at home with his family, on a mattress he purchased at Mattress Firm long before he joined our team.