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A Yawn is a largely involuntary (although controllable) response where an individual opens his mouth wide and breaths in air, followed by exhaling. A certain amount of noise is often associated with the latter part.

Yawning has been linked to being tired, a lack of oxygen, and boredom. It has also been noted that people have a tendency to yawn if they see others yawning.

A recent theory suggests that yawning is an effort to cool down the brain.[1]


  1. http://dsc.discovery.com/news/2008/12/15/yawn-brain-head.html