It may surprise you to find out that yawning is something that we
don't actually know much about. And by 'we,' I don't just mean the
Physics Van... In fact, no one knows much about yawning. One thing we
do know, though, is that it does appear to be 'contagious.' Not just
seeing other people yawn, but even thinking about it is enough to make
most people yawn. In fact, just reading your question was enough to
make me start yawning. (Can you read this whole answer with out
starting to yawn too?)
The old theory on yawning was that it was something that we did
when our brains needed extra oxygen. However, there has been a lot of
research lately showing that this isn't really true. Another fairly
common theory is that yawning is a way of showing that you're bored,
although there are a number of examples showing that this isn't always
true either. The only theory that I know of as to why yawning is so
'contagious,' is that we evolved the tendency to yawn as a way for one
person to signal others that they were about to change from one
activity to another. Unfortunately, none of these guesses have any
solid proof, so there's really nothing that can be said for certain.
If you'd like more information on yawning, check out HowStuffWorks.com's What makes us yawn?
. They also have links to lots of good pages on the same question.
(published on 10/22/2007)