Yawning Cools The Brain

At last we know why we yawn and why yawning is contagious... and it's got nothing to do with the length of my sermons :lol:

Yawning cools the brain

Tuesday, 16 December 2008
Jennifer Viegas
Discovery News


If your head is overheated, there's a good chance you'll yawn, according to a new study that found the primary purpose of yawning is to control brain temperature.

The finding solves several mysteries about yawning, such as why it's most commonly done just before and after sleeping, why certain diseases lead to excessive yawning, and why breathing through the nose and cooling off the forehead often stop yawning.

The key yawn instigator appears to be brain temperature.

"Brains are like computers," says Andrew Gallup, a researcher in the Department of Biology at Binghamton University who led the study, which has been accepted for publication in the journal Animal Behavior.

"They operate most efficiently when cool, and physical adaptations have evolved to allow maximum cooling of the brain."

He and colleagues Michael Miller and Associate Professor Anne Clark analysed yawning in parakeets as representative vertebrates because the birds have relatively large brains, live wild in Australia, which is subject to frequent temperature swings, and, most importantly, do not engage in contagious yawning, as humans and some other animals do.

Contagious yawning is thought to be an evolved mechanism for keeping groups alert so they "remain vigilant against danger," says Gallup.

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