Why do we yawn?

billzhao

Many people believe that we yawn because we are bored or sleepy, or our brain needs more oxygen. An interesting case is that a jury member was fined 1000 dollars for yawning in court. You may remember the picture of a yawning child behind President Bush who was delivering a speech.  

But certain aspects of yawning remain even more mysterious. Fetuses, for instances, have been observed yawning in the womb, yet it’s known that they don’t take oxygen in through their lungs. And yawning seems to be a symptom of multiple sclerosis and other medical conditions, for reasons unclear.

  O" H; `5 M9 s; oAnother puzzling phenomenon is that some male animals, men included, yawn in association with penile erection (although it’s presumptuous to assume they’re bored with their sex lives).

What do you think?

# q# c9 \5 u5 f) o% V0 g/ B[ 本帖最后由 billzhao 于 2008-9-22 22:30 编辑 ]

Xbfeng

It is impolite if you are yawning in public. But you can't help yawning.
In this case, you may have to use your hand to cover your mouth.

xb.su

You should never yawn at that time. haha