There are many things that science has found a way to explain, even if the "explanations" are temporary, and last only until a better explanation has been found. But some of the curious things we do as human beings still – at the beginning of the 21st century – have no known explanation, and remain as much a mystery now as they were centuries ago.
One of these, fascinatingly enough, is yawning. Scientists used to believe that it was an involuntary reflex that happens when our bodies feel the need to fill our lungs with oxygen or rid them of excess carbon dioxide. Well, that theory was shot down 25 years ago, when a researcher named Robert Provine, from the University of Maryland, decided to conduct the obvious experiment. He put test subjects in controlled-atmosphere rooms that he had enriched either with additional oxygen or additional carbon dioxide, and then watched carefully to see whether they yawned more often, or less often. Surprise…neither happened. The oxygen and carbon dioxide content of the air in the room – and therefore, logically, in the subjects' lungs – didn't affect their "yawning rate" at all.
Other theories of yawning
In the years since, Dr. Provine and other scientists have spent time trying to figure out what yawning is, now that they're pretty sure what it isn't. One of the only tangible findings they've discovered is that yawning can be suppressed. You can try an experiment to prove this to yourself at home if you like – next time you feel like yawning, either pinch your nose to hold it closed or grit your teeth. Chances are you'll find what Provine and his researchers found, that you can't yawn; they describe this as "the motor program" that is yawning not being able to complete itself unless you are able to inhale through your mouth and gape your jaws wide.
Another short-lived theory was proposed by Andrew and Gordon Gallup of Princeton University, who did experiments in which they found that yawning can be suppressed either by adjusting the room temperature or by applying a cold pack to the forehead. They then theorized that we might yawn to instinctively try to cool down our brains. This theory (as well as the oxygen/CO2 theory) were proven untrue when doctors started taking sonograms of pregnant women and discovered that fetuses yawn in the womb.
So are yawns contagious or not?
One aspect of the folklore surrounding yawning that does seems to be correct in that it can be triggered by drowsiness, stretching, boredom, or by seeing other people yawn. Scientists have even proved the truth of the title I chose for this article – yawning is so contagious that it can be triggered even by reading about it.
Yawning is even contagious in other animals. Studies have shown that chimpanzees and baboons yawn when they see others yawn. Suspecting that in animals yawning might be an indication of empathy with other animals, researchers at Emory University in Atlanta took videos of chimpanzees yawning, and found that they "caught" yawning from other chimps who were part of their "in group," but not as much from those part of their "out group," with whom they had less interaction or affinity. But in humans, contagious yawning doesn't really feel like a form of social bonding or increasing empathy; it's just an involuntary reaction that happens when we see others yawn. So yawning and why we do it still remains a mystery.
One theory is that yawning is triggered in the brain by the hormone oxytocin, released when we experience pleasurable and empathetic actions such as cooperating, touching, or kissing. This could, in fact, have something to do with empathy, because the increased oxytocin triggers the release of the neurochemical dopamine, our bodies' own "feel good" chemical. So it is logical to assume that the yawning could possibly be not the result of boredom or loss of interest, but the result of increased pleasure, and something that gives rise to even more.
Or at least that's what you should tell your significant other if they catch you yawning while cuddling with them. "It's not you, honey…it's my oxytocin levels…yawning just shows how much I appreciate you. If you really love me, you'll yawn back."
Yeah, right…that'll work.