I heard somewhere that yawning may be a sign of agression: You are challenging me, so I yawn and show you my big scary mouth that I could kill you with: I am dominant. Then you feel the distinct and overwhelming need to yawn back, You are dominant. You are just as capable of killing me as I am of killing you. So there.
Responses:
Waldorf and Statler
Well, if that's true, this website certainly has a knack for making me want to "assert my dominance."
Waldorf and Statler
Really? I'd say we assert our dominance over this website every time we say something halfway intelligent!