Why do we yawn?

Nowadays there are few things we humans do that scientists don’t have explanations for.

Dr. Robert Provine, at the University of Maryland, is an advocate of what he calls “sidewalk neuroscience,” that is experiments anybody can do at home without special equipment. However, he hasn’t been able to figure out why we yawn.

I remember this topic being discussed this in one of my high school classes in General Science. The teacher said that it serves to clear our lungs of carbon dioxide, enabling them to replace it with oxygen. That seemed to make sense. Having too much CO2 and not enough oxygen might make me sleepy.

However, appearing to make sense doesn’t make it true. Dr. Provine did the obvious experiment. He enriched the oxygen or the carbon dioxide in the air breathed by experimental subjects. There was NO increase or decrease in yawning compared with control subjects breathing normal air. Further study of yawning has found no obvious need, function or effect.

We have learned a bit more about it, however. A recent study confirmed that babies who open their mouths in the womb are indeed yawning, not just gaping. This was long suspected and wipes out the theory that yawning is about filling the lungs with oxygen or emptying them of carbon dioxide.

Dr. Provine learned something else by asking people to pinch their noses or grit their teeth while yawning: the “motor program” that it starts will not run to completion unless you can inhale through your mouth and gape your jaw wide.

Another set of experiments found that yawning is suppressed by a cool pack strapped to the forehead or by summer temperatures that are higher than body temperature.

This led to the hypothesis that perhaps the purpose of yawning is to cool the brain by inhaling air. But then why do fetuses yawn?

As a folklorist, I believe (without benefit of science) that yawning is triggered by boredom, drowsiness, stretching or other people yawning. Yawning is so contagious and suggestible that even reading/writing an article about it can trigger the reflex … excuse me.

Perhaps the main purpose of yawning is to remind us how mysterious human beings still are, even to themselves. Reading about all these studies has led me to ask whether we have a surplus of scientists or a shortage of important problems for them to work on.

Happy birthday Thursday to Nola Wortman, Tammy Peters, Dahled Doggins Wiley, John Dannel III, Evelyn Johnson, Laura Shaw, John Cooper and LaVonda Jacobs, all of Sherman; Jeannie Sikes of Edmond, Okla.; Brittainey Ertel of Fort Worth; Ralph Weldon of Ambrose; Cathy Powell of Whitewright; Liz Clinton of Anna; Suzanne Bailey Dougherty of Arlington.