Cool Weather Coming? Big Yawn

Scientists have a new theory on a contagious mystery of biology

Even puppies yawn. Awww

Dogs do it. Cats do it. Even fish and guinea pigs do it. If the guy next to you at a dull meeting at work does it, chances are you will, too. But as common as it is to yawn, scientists have never quite been able to pin down why so many animals have the contagious habit of opening their mouths super-wide to take in and then exhale a deep breath. Now, a pair of researchers at Princeton say they have a clue.

After conducting a study that showed the brain temperature of rats declining after they yawn, Andrew Gallup and Omar Eldakar tested the frequency of yawning in 160 people in Tucson, Arizona—80 in summer, 80 in winter. Their results showed we’re much more likely to yawn when the weather is cold than when it’s warm. This would tend to indicate that yawning serves a thermoregulatory function: When the air is chilly and we suck in a giant gulp of it, the heat exchange inside our heads cools down our brains. The act of yawning also increases blood flow to the brain via the stretching of our jaws (and, often, other parts of our bodies; the act of simultaneously yawning and stretching one’s extremities is known as “pandiculation,” a term politicians should fling about more often: “My opponent, a known pandiculator, would have you believe otherwise.”)

Gallup and Eldakar say yawning is counterproductive when the surrounding air is already warm; you can’t cool the brain down with hot air. In their experiments, half of all winter-studied subjects yawned when shown photos of other people yawning; in summer, less than a quarter of the subjects did. (Completely apropos of nothing, dogs yawn when presented with strangers who yawn, but not when those strangers merely open their mouths. Dogs also yawn when they’re confused, which is much of the time.)

The results of the research, funded by a grant from the National Institutes of Health, could help scientists better understand medical conditions whose symptoms include frequent yawning and thermoregulatory disfunction, such as epilepsy and muscular dystrophy.