The Long Tail and the Limits to Training

In trying to make sense of intelligent behavior, it is tempting to try something like this: we begin by looking at the most common cases of the behavior we can think of, and figure out what it would take to handle them. Then we build on it: we refine our account to handle more and more. We stop when our account crosses some threshold and appears to handle (say) 99.9 percent of the cases we are concerned with.