“A yawn may not be polite, but at least it is an honest opinion.” — Unknown

Let me first define a yawn.  A ‘yawn’ is a reflex of simultaneous inhalation of air and stretching of the eardrums, followed by exhalation of breath.  Now, for your next game of Scrabble, the definition of ‘pandiculation’: “The act of yawning and stretching simultaneously.”  Yawning is as natural as scratching our heads.  It begins before we are even born, and is common among many animals.  For generations it has been thought to be a signal of fatigue or boredom.  Ranked somewhere near the top of the list of rude behaviors, usually occurring at the most inopportune time, it turns out that science may have now answered the age-old question of why we yawn.  For decades scientists believed yawning helped replenish low blood oxygen levels.  However, a recent scientific study has provided us with what appears to be a more reasonable explanation, as well as a glimpse into the mystery of the contagious yawn.

State University of New York at Albany psychology professor Gordon Gallup, and his son Andrew Gallup, a researcher in the Department of Biology at Binghamton University, led the study.  It turns out the key yawn instigator appears to be brain temperature, and in a sense the yawn is like the brain’s air conditioner.  This cooling notion arises from the fact that the brain uses considerable calories to operate, about one-third of our caloric intake, and that kicks off a lot of heat.  Heat, it turns out, is a problem for the brain.  According to the elder Gallup, “Brains are like computers.  They only operate efficiently and effectively when they’re cool.  And, therefore, there are some very intricate cooling mechanisms that serve to regulate the temperature of the brain.”  This is where the yawn comes in.  The idea is that when a person’s brain temperature becomes too elevated, it triggers a yawn.  As a person yawns, large volumes of cool air pour into the lungs through the nose and mouth, cooling down the blood in the capillaries. That causes heart rate and blood pressure to increase, and this in turn sends a cool wave to the brain.  The idea is that the fresh, cooler air will reinvigorate the brain, allowing it to better focus on the matter at hand.

Gallup and his son tested their theory by creating an experiment where students were asked to watch a film of other people yawning.  When they held a cool compress to their head, or breathed through their nose — a natural brain coolant given the sinus cavities’ proximity to the brain — they did not yawn at all.  But, if they breathed normally or held a warm compress to their heads, they were far more likely to yawn.

This finding solves many of the mysteries about yawning, such as why it is done most often just before and after sleeping, why breathing through the nose and cooling off the forehead often stop yawning, and why certain diseases lead to excessive yawning.  For instance, patients with multiple sclerosis (MS) often experience bouts of excessive yawning and MS involves brain temperature regulation dysfunction.  Also, increased episodes of yawning frequently precede the onset of seizures in patients with epilepsy, and can often predict the onset of headaches in migraine sufferers.

We have known for quite some time that exhaustion and sleep deprivation increase brain temperature and produce excessive yawning.  If the air around us is cooler than brain and body temperatures, taking it in quickly cools the brain and may even alter blood flow. Prior studies have revealed that yawning leads to a heightened state of arousal.  So, a morning yawn may actually function somewhat like a cup of coffee in providing the brain with a bump of energy.

But, what is behind contagious yawning?  Contagious yawning is thought to be an evolved mechanism for keeping groups alert so they remain vigilant against danger. According to Andrew Gallup, “During human evolutionary history, when we were subject to attacks by a group, the ability to detect danger would have had a critical relationship to your ability to respond to it on a moment to moment basis.  If everyone yawns in response to seeing someone yawn, it reinstates an optimal level of vigilance on the part of people in the group.”

In the future, researchers may focus more on brain temperature and its role in diseases and their symptoms.  But this study on yawning changes the popular notion that yawns are simply signs of boredom.  In fact, in some ways, odd as it may seem, as Gordon Gallup points out, “yawning more accurately reflects a mechanism that maintains attention, and therefore should be looked at as a compliment!”    If the Gallups’ theory is correct the yawn could someday be seen in a whole new light, and the habit of discretely trying to stifle a yawn during a conversation could become a thing of the past.