The Conditions of Learning

Since it is manifestly impossible to observe directly what happens in the organism when it learns, psychological studies of the phenomenon are confined to an analysis of external conditions favoring learning. These studies have given us a number of "laws" from which the nature of learning itself is inferred. We shall need to examine each law briefly before considering its adequacy as a basis for theorizing. The most generally accepted is the law of contiguity, which states that, in order for response to one stimulus to become associated with another stimulus, the two excitants must fall within a given time interval. For lower animals this interval is a matter of a few seconds; but in man, due to mediated processes, the interval may be quite prolonged.

The law of contiguity can be demonstrated in a number of ways. At present, the conditioned reflex, as used by Pavlov, is an especially popular technique. A dog, upon which a permanent salivary fistula has been made, is trained to salivate to a previously inadequate stimulus (bell) through the simple expedient of presenting this stimulus together with one (food) which is adequate to evoke such response. The dog is placed in a harness and the salivary flow is directed by means of a tube to a recording room, where it is counted by drops. This technique can be used with human subjects by placing a rubber suction cup over the parotid gland ducts inside the cheek; but a more common type of experiment utilizes some readily available motor response, such as the kneejerk, the Achilles jerk, the eyelid reflex, the pupillary reflex and the galvanic phenomena.

The features of the conditioning process of especial interest are: (1) the fact that the indifferent stimulus is presented before or simultaneously with the unconditioned stimulus in order for it to be most effective; (2) the necessity of making the conditioned stimulus sufficiently intense; (3) the phenomenon of experimental extinction, or the failure of the conditioned stimulus to elicit response if repeated by itself a number of times; (4) the production of secondarily conditioned reflexes through the presentation of the newly conditioned stimulus with one which is still ineffective; and (5) trace conditioned reflexes, which take place when the interval between the presentation of the conditioned stimulus and the unconditioned stimulus is considerably lengthened. Several explanations of conditioning and the law of contiguity will be presented in a later section. Here we have been interested in a method of demonstration, not in any connection which that method may have with hypothetical formulations.

The law of use, which states that contiguous stimuli and responses are linked together in a firmer bond as a result of repetition, is still a subject of controversy among psychologists. It is not the usefulness of repetition which is questioned, but its universal importance. Some connections are learned as the result of a single presentation. Furthermore, the responses which improve through use are very complex; and the learning curve may be as well explained by assuming that totally new connections are made at different trials as by assuming that the same connection is involved in all cases, and that its effectiveness improves gradually. It has been pointed out many times that improvement in any complicated skill is due mainly to establishing new ways of reacting rather than to perfecting old ways. Another bit of negative evidence is the fact that repetition of some acts breaks down former associative connections.

In conditioned reflex experiments, responses to a formerly inadequate stimulus are elicited with progressively greater ease, provided they are reinforced occasionally by the original or "unconditioned" stimulus. Since these experiments apparently involve the connection of a single stimulus and response, they are frequently cited as evidence of improvement in conduction over a single path as a result of exercise. But it is significant that after removal of the unconditioned stimulus, as in experimental extinction, repetition weakens rather than strengthens the conditioned reflex connection. Pavlov has argued that this is due to a development of inhibitions in the conditioned pathway, but he is using the term here in a most objectionable sense. We are not dealing with the suppression of one activity by another but with a suppression which is the result of repetitions of stimuli. This phenomenon looks more like the adaptation or fatigue of the end-organs than the competition and rivalry of neural arcs. Experimental extinction is, therefore, in opposition to the law of use. This does not mean, of course, that exercise is not important in learning; it merely indicates that the law is capable of various interpretations.

The law of effect states that connections between stimulus and response are fixed upon the basis of their "satisfyingness." This law offers more difficulties in the way of physiological interpretation than does either of the foregoing. The original version of it states that pleasurable connections are "stamped in," whereas painful connections are "stamped out." This version is particularly open to criticism because it assumes that the consequence of every learning has been pleasant, whereas unpleasant experiences are sometimes retained more easily than pleasant ones. A less objectionable view maintains that those responses are fixed which "consummate" an organic tissue need. As stated in a previous chapter, tissue needs supply a mass of afferent impulses which persist until satisfaction is obtained; either cessation or persistence of these impulses fixes a dominant response. There is no question that consummatory reactions do become fixed, but the mechanism involved is in no wise clear.

There are numerous other conditions of learning, such as recency, frequency, and vividness; but these are secondary to those cited above. For example, it is probable that recency and frequency are effective conditions for learning only when they intensify or vivify the stimulus for the learner. Vividness itself cannot be measured in terms of the objective intensity of the stimulus, but only in terms of inferences based upon the reactions made. All we can say is that such factors are important, and that a complete theory of learning must account for their influence.