According to a new study in Frontiers in Evolutionary Neuroscience, yawning may cool your brain when the air outside is cooler than your body.
Researchers analyzed how frequently people yawned in the summer and the winter in Tucson, Arizona. They found that people were more likely to yawn in the winter than the summer, when temperatures outside were close to or higher than normal body temperature. The researchers say that your wide-open mouth allows your body to exchange heat with the cooler air, which is why taking in warmer air doesn’t have any cooling effect.
So why does your brain need the occasional cooldown in the first place? “The brain is exquisitively sensitive to temperature elevation, and cognitive function becomes impaired during hypothermia,” says Andrew Gallup, a postdoctoral research associate at Princeton University and lead author of the study. “Thus, brain temperature regulation is essential for optimal mental processing.” In other words, your brain works better when you’re not hot-headed.
Here’s what we wondered: Does your brain temperature really fluctuate enough that you’d ever notice? Gallup lists a number of factors that affect your brain temperature, like how fast your blood flows and the heat produced by all of your other body processes. Thus, you may only notice extreme reactions, like when you step into a cold freezer and start shivering. But your body has many ways of maintaining a relatively constant temperature, says Gallup, and yawning is one of them.
In the future, confirmation of yawning’s brain-cooling effects may help researchers better understand conditions like multiple sclerosis or epilepsy, both of which are accompanied by frequent yawning.
And of course, the next time you find yourself trying to stifle a yawn at a business meeting, you can just tell your boss that your brain needed a little cooling.