a) If you're yawning, you are generally in an area with slightly low oxygen levels. (eg classroom, bus, indoor area with lots of people) Since yawns are to get extra oxygen into your system, and everyone else is in that same low oxygen environment as you, they'll yawn too.

b) When you yawn, it takes in more air & uses more oxygen than normal breathing. You are taking away a greater amount of oxygen from someone else. Then they need to yawn to make up for that. & vice versa.

Yawning. A vicious cycle.

There was an article on newscientist awhile ago about how it may have been used by the older members of a group / tribe to indicate to the younger ones it was time to go to sleep which is a nice idea
Beats stuffing them at the back of the cave

I just thought it was when you were tired. Well yawning also helps stretch your muscles in the morning when they're stiff.

You yawn in the mornings because ur body is not taking deep enough breaths because uv just woken up pretty much and your probably not fully awake. Yawning is supposed to remind ur body to get into a regular breathing pattern again. That's also why you yawn when ur tried because ur body starts slacking off and u dont take enough oxygen into your lungs. Hence why yawns are gigantic breaths.

*yawns* after reading this topic i cant stop yawning! grrr!

Isn't there some thing that if you yawn with your eyes open, your eyeballs fall out? or is that sneezing?! I'm confused. . . something tells me it isnt true. . . heh. . heh . . . .. ..