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Why do we yawn?

Yawning, more scientifically called pandiculation, is a reflex of simultaneous inhalation of air and stretching of the eardrums, followed by exhalation of breath. Aside from humans, other animals also exhibit yawning.

There are several theories as to what causes yawning and why we do it.  However, none of them has been empirically substantiated.

Scientists tend to agree, though, that a yawn regulates the carbon dioxide and oxygen levels in the blood and can be triggered either by fatigue, or by sheer boredom as, at those times, breathing is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system.

 

When one yawns, his or her alertness is heightened, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.

This quite plausible theory of yawning falls short of explaining many aspects of yawning. Scientists explain away the "contagious" nature of yawning, that is when one person's yawn triggers another nearby to yawn, as due to the power of suggestion, but are at a loss when attempting to explain why yawning occurs excessively in patients with lower brain stem damage or with multiple sclerosis.

Other unlocked mysteries include why fetuses in the womb yawn, when it is a well-known fact that they do not intake oxygen into their lungs until after live birth, or why individuals with high concentrations of oxygen in their blood streams yawn.

Until these questions are answered, do not assume that a person who yawns in your presence is bored with what you are saying, or suffers from exhaustion.

 

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