The biggest question for me is "How is it possible for children, young human beings, to learn as much as they do as quickly and as effectively as they do?" We've known for a long time that human children are the best learning machines in the universe. But it has always been like the mystery of the humming birds. We know thast they fly, but we don't know how they can possibly do it. We could say that babies learn, but we didn't know how.