Perceptual learning; differentiation or enrichment?

The term "perceptual learning" means different things to different psychologists. To some it implies that human perception is, in large part, learned—that we learn to see depth, for instance, or form, or meaningful objects. In that case the theoretical issue involved is how much of perception is learned, and the corresponding controversy is that of nativism or empiricism. To others the term implies that human learning is in whole or part a matter of perception—that learning depends on comprehension, expectation, or insight, and that the learning process is to be found in a central process of cognition rather than in a motor process of performance. . In this second case, the theoretical issue involved is whether or not one has to study a man's perceptions before one can understand his behavior, and the controversy is one of long standing which began with oldfashioned behaviorism. These two sets of implications are by no means the same, and the two problems should be separated. The problem of the role of learning in perception has to do with perception and the effect of past experience or practice on it. The problem of the role of perception in learning has to do with behavior and the question of whether we can learn to do something by perceiving, or whether we can only learn by doing it. The questions, then, are these: (a) In