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Gradual Versus Sudden Solutions
to Discrimination Problems


Excerpt from Kenneth Spence's paper "Gradual versus sudden solution of discrimination problems by chimpanzees"
Journal of Comparative Psychology, 1938, 213-224

Kohler, in his 1925 paper likewise considered sudden solutions in the learning of discrimination problems. While he pointed out that discrimination learning is usually a slow gradual process even in the anthropoids, he nevertheless claimed that learning is probably quite different in cases in which the solution is sudden. The occurrence of such sudden solutions is, moreover, evidence to him that the learning involves more than mere associative processes or, to quote him: 'We do not well describe experiments of this type by saying, as we usually do, that an animal in such a situation learns to connect certain stimuli with certain reactions and that the connection is "stamped in". This formulation of the process gives too much importance to the memory or association side of the problem, and it neglects another side of it which may be even more important and more difficult'(2). This neglected aspect of the problem, according to him, is the process by which the sensory field becomes organized, or rather reorganized, during learning, and it is this part that is responsible for the sudden solutions or insights in learning.

But are such instances of sudden jumps in the learning curves of animals evidence either for the existence of an insightful factor in learning, or for the inadequacy of the view that learning consists in the formation of stimulus response connections by a repetitive process of reinforcement and non-reinforcement? In the opinion of the writer, both parts of the question are, as yet, to be answered in the negative. To say, as the Gestalt psychologists do, that such learning involves the development of insight is merely to restate the problem in new terms. No satisfactory theoretical account of how such an insight factor operates to produce such sudden learning in discrimination problems, or for that matter any other type of problem, has ever been given by its Gestalt proponents. The association theorists, of course, are in exactly the same position, for they have never given a satisfactory theoretical account of this phenomenon. It does not logically follow, however, that an adequate theory cannot be developed on association principles.

The writer recently presented a theory of the nature of discrimination learning, based on association or conditioning principles, which was shown to be capable of explaining the various phenomena known to be characteristic of the presolution period of learning (5). Quite in contrast to the Gestalt configuration interpretation, this theory conceives discrimination learning as a cumulative process of building up the strength of the excitatory tendency of the positive stimulus cue (i.e., the tendency of this stimulus to evoke the response of approaching it) by means of the successive reinforcements of the response to it, as compared with the excitatory strength of the negative stimulus, responses to which receive no reinforcements. Learning is completed when the difference between excitatory strengths of the two cue stimuli is sufficiently large to offset always any differences in strength which may exist between other aspects of the stimulus situation that happen to be allied in their action with one or other of the cue stimuli; for example, such differences as may exist between the excitatory strengths of the food boxes on which the cue stimuli are placed. In the presentation of this theory, no consideration was given to the problem of the occurrence of sudden solution in discrimination learning.

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