Archive for Monday, March 23, 2009


The big yawn: Why do we do it? Even scientists aren’t sure

March 23, 2009


Let’s start at the beginning.

Who yawns? Everybody. Not just people, but cats, dogs and fish do, too!

What is a yawn?

It is an involuntary action during which you open your mouth and breathe deeply for, on average, 6 seconds. “Involuntary” means you don’t think about doing it; you just do it.

Why do we yawn?

Scientists aren’t really certain what triggers a yawn. They aren’t even sure what part of the brain causes yawning.

We know that people yawn when they are tired or bored, but they also yawn when they aren’t. In fact, athletes sometimes yawn before competition, when they are the opposite of tired and bored. Babies in the womb yawn, too.

One theory is that yawning is a way for the body to become more alert by taking in more oxygen. A yawn increases the heart rate, forces carbon dioxide out of the lungs and bloodstream, and brings oxygen to the brain.

But one study showed that volunteers given a lot of oxygen did not yawn any less than before, and those exposed to a lot of carbon dioxide did not yawn more.

Another theory is that human ancestors used yawning as a form of communication and that the action has remained with us. Baboons living in groups, in fact, signal that it is time to go to sleep by yawning a lot.

Do we yawn when we see someone else yawn?

Scientists say yes, but — you guessed it — they aren’t sure why.

It might be the power of suggestion. In one study, subjects were more than twice as likely to yawn while watching a series of yawns as while watching a series of smiles.

Yawns, like every human action, originate in the brain; and scientists are still unlocking the mysteries of how the brain works.

There is still a lot that scientists have yet to figure out, even something as seemingly simple as why our eyes sometimes twitch. Or why we hiccup.

So, did you read this entire article without yawning? (We bet not!)


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