As a substitute for knowledge acquisition and engineering machine learning is frequently thought of as free. But you can't just release an AI (or a human infant) into the wild. As John Andreae has observed with his AI "...run on its own. It quickly runs out of memory...it is better for PP to be 'taught' by a teacher." (Associative Learning, Imperial College Press, 1998, pg 13) With Asa H I find that what is taught and the order in which it is presented is quite important.