This is by Jack Valko
Special to http://ABCNEWS.com
The physiological theory states that a yawn is a reflex that occurs when your brain recognizes a need for more oxygen. Yawning is contagious because everyone in a room is likely to be shy on fresh air at the same time. A yawn may also be stimulated by external cues, much like watching someone eat can make you hungry.
The boredom theory is based on the assumption that if everyone finds something boring, they will yawn. This doesn’t explain why we yawn when bored, however, unless it’s an instinctive way we use body language to say something is uninspiring.
The evolutionary theory says that we yawn to display our teeth, a behavior left over from our more primitive beginnings. Yawning could act as a warning to others. These days it would seem an obsolete display, since we’ve supposedly become more civilized.
Since no one has figured out exactly why yawning seems to be contagious, the real cause will remain a mystery for now. I bet you’re about ready to yawn right now. If so, I hope the boredom theory is wrong — otherwise I might be out of a job.