Does yawning help cool the brain?
So why do we yawn? A common belief is that it helps increase the brain's oxygen supply, but no research has been able to prove that. Now a study suggests a different purpose--it may be done to cool the brain.
Sleep cycles, cortical arousal and stress can all change the temperature of the brain. Yawning, according to the researchers, is a way to keep brain temperature balanced. They focused on determining if it only occurs when the air is within a certain temperature range.
For the study, researchers measured contagious yawning frequency of pedestrians outdoors in Vienna, Austria, during the winter and the summer. They then compared results to an identical study done in the arid climate of Arizona. The pedestrians were asked to view a series of images of people yawning, and then self-reported their own yawning behavior.
Results showed that in Vienna, people yawned more in the summer than in the winter, but people in Arizona yawned more in the winter than the summer. Therefore, it was not the seasons or the amount of daylight hours experienced, but the optimal thermal zone that encouraged yawning. The optimal ambient temperature for yawning was found to be around 20 degrees Celsius or just under 70 degrees Fahrenheit.
Researchers say yawning cools the brain, but generally doesn't happen when the air is as hot as the body or when temperatures are freezing.