Yawns.

Seriously, why is yawning contagious? The Mythbusters proved that it is. And so does, you know, everyday life. I just made someone yawn just by yawning on the phone. And why do my eyes water when I yawn? Is that normal? I had a boyfriend once that said that wasn't normal. I read somewhere that yawning is actually a sign of not getting enought oxygen. So what does that have to do with being tired? I really don't think I am so tired that I'm forgetting to breathe enough.