Now, don't anyone flame me for this one. I'm just telling you an idea concerning the "group yawning effect" that I came across a while back.
It runs parallel to the "group gag reflex". You know, when one person gags or vomits, invariably other people (me included) will feel like gagging too. The theory I heard for that was it is a survival mechanism. When we were monkeys or early humans (or whatever- I don't want to get involved in an evolution vs creation debate) presumedly the group would have all been eating the same thing. If it was spoiled or poisonous it would have been imperative for the group to quickly vomit up what they were eating if one member became ill.
Likewise, with the yawning thing. When it got evening and the alpha male or Mongo the chief decided it was time to go "beddy bye" then it was time for all the little monkeys to go beddy bye. This increased their survivability by keeping the noise level and activity to a minimum while nocturnal predators were roaming around. So the yawn is perhaps a signal that we are hardwired to pick up on.
I don't know how much credence I give it and like all these "theories" it can't really be proved anyway so it relegates it to a mere interesting conversation piece. I do know that sometimes in the Army in a large barracks I would be the first one awake. I'd just lay there quietly so as not to disturb my fellow soldiers. But invariably, someone else would soon wake up and then another and another- even if nobody was making any noise and it wasn't time for us to wake up. Pretty soon everybody would be kicking around in their bunks. So maybe we are programmed for these types of group input? Who knows.
Now, I've read that yawning is a 'stay awake' mechanism.