Most people seem to be quite sure they understand yawning. They think it is caused by the need for oxygen, or boredom, or sleepiness. A group of medical scientists (Walusinski 2010) have upset this applecart. They found no evidence for any of these three causes. They did, however, have one positive finding: yawning is contagious. When we see others yawning, we often want to join them.
Suppose that yawning is a way of resolving the physical tension that comes with fatigue and illness. If that were the case, it would be important that we yawn when we need to, even if we are in the presence of others who might think it rude. The fact that yawning in company is usually considered rude helps explain contagion: we hold back yawns until we are alone or with others who are yawning.
I have known of many cases that suggest that yawning helps resolve the physical tension that comes with illness. The following is one example. A middle-aged man, usually healthy, was suffering from a rare skin disease that covered most of his upper trunk and some of his arms and legs. The disease was very painful for some time, since it took several months to find a physician who knew how to treat it.
By the time it had covered a large area of skin, the illness had become so painful that it was difficult to sleep. However, after several sleepless nights, he accidentally discovered that yawning reduced much of the pain. “By faking some yawns, I could induce fits of real yawning, then sleep. At times the tearing was so great that I first had to put on dry pajamas. To the annoyance of my family and friends, I have been a yawner ever since.” The presence of tearing appears to be important, since all of the cases I know of include it.
An everyday exercise would be a yawning yoga. If you fake a few yawns, you may have a fit of enjoyable yawns (and if others are present, spread the contagion to them).
Walusinski, O. (Ed.) 2010. The mystery of yawning in physiology and disease. Basel: Karger.