In other circumstances, though, babies act as if they don't know very much about what has happened to objects that disappear. Suppose you show a six-month-old some wonderfully fascinating thing, a watch or a bunch of keys. He grins and bounces excitedly and starts to reach for it. Now cover the keys with a washcloth. The baby stops dead in his tracks. The excited glee is replaced by a sort of blank puzzlement. Pull off the washcloth and the glee returns.