Why does yawning variety you yawn?

How does this work, i heard you yawn because you have need of more oxygen, but why do you need to yawn when you see ancestors yawn, or when you talk around yawning, or even when someone yawns when your on the phone to them??
ThanksWhy does yawning variety you yawn?
yawn.
your question made me yawn
thats a moral question !
hmmm... it could be that your tired and seeing other those yawn, makes you yawn.
To be immaculately honest i have no concept. But it really makes you dream up.
it's cause you entail a nap
Woah dude i yawned when i answered this...SWEET


2 points and i dunno
I hold often wondered in the order of this myself. It will be interesting to see the answers.
I always find it strange how when someone near you yawns you will yawn as okay.
lol just yawned reading your interview & i don't know why but now i can't stop
I yawned when I READ the cross-examine. LOL
Sure hope someone can answer this one!
:)