I prefer to look at kids 0 - 3 or 4 as acid heads. Certainly for the first year almost everything is brand new and, "Oh wow, man" worthy to them ... sights, sounds, smells, tastes, ... everything.
They are also absorbent little sponges, just sucking up and in everything they receive ... especially language.
The true chucklehead is the younger teenage boy ... 12 - 15 or 16 ... now THERE is a specimine of life-form that defies logic, reason and perhaps even definition.
My 9 year old grand son is precocious, he's already there.