If you ask people why they yawn, the most typical answer will be "because I'm tired." But sleepiness and boredom might not be the real reasons behind yawning. It actually might be a way of getting rid of hot air.


That's the finding of Princeton researcher Andrew Gallup and the University of Arizona Omar Eldakar. The pair have found that yawning frequency is correlated with what season it is, and people are more likely to yawn when their body temperature is greater than the heat around them. They argue that yawning is actually a way for our bodies to regulate brain temperature, and the apparent link to fatigue or boredom are just coincidental to that process.

Gallup explains:





Gallup and Eldakar tested this hypothesis by measuring the yawn frequency of 160 Arizona pedestrians, eighty of whom were tested during summer - when average temperatures are 98.6 degrees Fahrenheit, just like our internal temperature - and during winter, when it's a relatively mild 71 degrees. As Gallup explains, the results showed a clear season variation:



Via Frontiers in Evolutionary Neuroscience. Image by robef on Flickr.