What the heck is so funny?

We are having trouble uploading videos right now so I guess that means I actually have to write something.
One thing that has taken me off-guard in the last week is the Random Laugh. We have no idea what makes Riley smile at this point because she does it at odd times and almost always with her eyes closed. What is she thinking about and what experiences that she is reflecting on could make her smile? Is it just a reflex or is she actually happy? These are things you ponder at 3:30 in the morning when you are trying to stay awake and hold a baby and bottle.
Even stranger than her eyes-closed smile is the occasional time when she breaks out into laughter. Again, what is possibly funny to someone who is two weeks old? She hasn't even been alive long enough to see the new episodes of shows since the writer's strike ended. The strangest part is that on the rare occasion that she does laugh, she is staring past you or has her eyes closed, so it has nothing to do with any entertainment value we might have. Maybe she is just getting the jokes we made a few days ago or perhaps its a maniacal laugh of power upon the realization that we are at her beck and call, 24 hours a day. Either way, I'm sure it will only be one of the many mysteries we will encounter in the next little while.
-Chris