Causes of Yawning
Cats, humans, dogs and monkeys all yawn. So do snakes and other reptiles, on occasion. Why do we yawn? There are several reasons for this involuntary reflex, ranging from evolutionary group-think to the unconscious need to introduce more oxygen to the bloodstream. Science is still torn as to why we yawn, but there are many doctors and scientists on the case.
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What is a Yawn?
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Yawning is something that everyone does on an involuntary basis. In fact, one yawn may set off a chain reaction of yawns throughout a group. Andrew Gallup, a researcher at Binghamton University, says, "Yawning more accurately reflects a mechanism that maintains attention, and therefore should be looked at as a compliment!" A yawn is, in fact, a very deep inhalation. According to Scientist, Interrupted, "Yawning is a familiar behavior characterized by a large gaping of the mouth, accompanied by a deep inhalation." The diaphragm is pushed down, but comes back up and presses some of the newly inhaled air back out.
Function of the Yawn
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There are a lot of reasons for yawning, and they are not all related to fatigue. One theory behind yawning is that it works to reduce the amount of carbon dioxide by bringing in fresh air and quickening the heart rate to flush out the system. Other theories include the yawn as an evolutionary show of (literal) teeth, and the time-tested yawn as an expression of boredom. However, none of these really explain the yawning that happens at times of tension or nervousness. Robert Provine, professor of science at University of Maryland, says, "Monkeys make yawn-like gestures that we know are hostile or aggressive actions. Subordinate animals never yawn in the presence of the alpha male."
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Medical Conditions and Yawning
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The website Wrong Diagnosis lists 10 different diseases or illnesses that can cause excessive yawning. Among them are stroke, stress, migraines, heart conditions and epilepsy. It occurs along with other symptoms, and isn't a sign of any particular illness in and of itself. "The New York Times" states, "Yawning is a normal response to fatigue and drowsiness, but excessive yawning can be caused by a vasovagal reaction. This reaction is caused by the action of a nerve, called the vagus nerve, on the blood vessels." Excessive yawning can also show up with anxiety and depression cases.
Who Yawns?
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Many vertebrates yawn. People have seen pictures of big jungles cats like cheetahs and lions yawning. Mammals, as a rule, do yawn, but so do some reptiles. Some scientists think that reptilian yawning might be attributed to a need to lower brain temperature. Insects, however, don't yawn as much. The Wisegeek website states that it may do with their different respiratory structure. Because of the way that their respiratory systems work, they process oxygen through other methods that preclude yawning.
Expert Insight
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DuPage Medical Group otolaryngologist Dr. Terry Donat says that, "[Yawning is] one of the most complete pieces of evidence that we are not in complete control of our minds." He also believes that yawning isn't as much a function of introducing oxygen into the body as it is a marker of transition from activity to inactivity, or vice versa. Dr. Timothy McGee, a pulmonologist and sleep disorder specialist at Central DuPage Hospital, adds that sequential yawning habits among people and animals may be a throwback to our early days of herd leadership.
What is certain is that you have probably yawned several times reading this article about yawning.
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Resources
- Photo Credit 2007 fofurasfelinas / Creative Commons
