Babies have such a sensitive system that everything is new to them ~~ sights, sounds, and yes, even odors. And don’t forget the sense of touch - if you touch their cheek, they will turn their head in that direction because it is the signal for food.
If you let them grip your finger, it will seem as if they are trying to pull themselves up. And some may very well do that! :o]
He does punches to the face pretty good.