And You Thought it Was Because You Were Bored

We yawn when we’re sleepy, bored, or because we see someone else yawn. Some people yawn when they’re stressed. But why? It’s long been believed we yawn to increase the oxygen supply to the brain. However, a study published this week in Physiology & Behavior concludes yawning serves a different purpose: It cools our brains.
Led by psychologists Jorg Massen of the University of Vienna, and Andrew Gallup of the State University of New York College at Oneonta, researchers took their cues from previous studies showing increased brain temperatures precede yawns and equivalent decreases follow them. From this, they postulated we should yawn predominantly within an optimal range of temperatures.  The study, conducted during both winter and summer months on subjects in Vienna, Austria, and Tucson, AZ, finds that range to center around 20 degrees Celsius (68 degrees Farenheit).
Massen concludes that as a brain-cooling mechanism, yawning is not functional when ambient temperatures are close to that of the body, and may even have harmful consequences when it’s freezing outside.