" Early in the 19th-century, the behaviorist E. L. Thorndike performed a series of experiments that satisfied two generations of American psychologists that abstractions were not importantly involved in learning how to perform skilled tasks. He asked his subjects to perform a particular task for varying amounts of time (e.g., cancelling Os from a sentence, and then switched them to another task; cancelling adverbs from a sentence). He found that “transfer of training” effects were slight and unstable. Sometimes he found that performance of the first task enhanced the second, sometimes that it made it more difficult, and, often, that it had no effect at all. One would, of course, assume that performance on the second task would be improved if subjects learned something general from performance of the first task. Since they so often failed to show improved training, Thorndike inferred that people don't, in fact, learn much that is general when performing mental tasks. This meant that training was going to be very much a bottom-up affair, consisting of little more than slogging through countless stimulus-response associations. This conclusion has suffused deeply into American psychology, cognitive science, and education. Newell (1980), based on some similar failed efforts to find training effects for reasoning tasks, has asserted that learned problem-solving skills generally are idiosyncratic to the task. "