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Sunday, May 11, 2008
What Are You Yawning About?
It takes about six seconds. Slowly, you take in a deep breath, exhale more quickly, stretch out your arms, contort your face, and your narrowed eyes may tear a bit. You have just yawned, something that almost all vertebrate animals do many times a day by some estimates, 10 times per hour, though more often in the early morning and late evening. Does it mean you are tired? Bored? Trying to give someone a hint? 
As common as it is, little is known for sure about yawning, but it is probably a myth that yawning always indicates a need for sleep. It is true that people often yawn as they are ready to retire for the night; but it is also true that it happens when first arising in the morning, and at other times during the day depending on a variety of factors such as arousal level, distraction, and even seeing someone else yawning. Because breathing takes in oxygen and removes carbon dioxide, theories in the past about why we yawn centered on the assumption that it was a reflex in response to low oxygen or high carbon-dioxide levels. This theory lost favor after a study in 1987 in which volunteers subjected to high oxygen levels did not yawn less, and after high carbon dioxide exposure did not yawn more.
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21:51 Posted in Science | Permalink | Comments (0) | Email this | Tags: Yawning, Sleep, Science, USA, World, Blog, journal