If i understand correctly, pictures are removed because the notional participant has previous knowledge of how objects in the world look like. If that's correct, then a newborn baby in a library with pictures kept would be faced with a similar problem. Which are then the important differences between that notional newborn and an actual newborn in a normal family? I can think of (a) having physical objects to manipulate (b) feedback from other humans. Am i missing some obvious difference?