Are theories of learning necessary?

Certain basic assumptions, essential to any scientific activity, are sometimes called theories. That nature is orderly rather than capricious is an example. Certain statements are also theories simply to the extent that they are not yet facts. A scientist may guess at the result of an experiment before the experiment is carried out. The prediction and the later statement of result may be composed of the same terms in the same syntactic arrangement, the difference being in the degree of confidence. No empirical statement is wholly non-' theoretical in this sense, because evidence is never complete, nor is any prediction probably ever made wholly without evidence. The term will not refer here to statements of these sorts but rather to any explanation of an observed fact which appeals to events taking place somewhere else, at some other level of observation, described in different terms, and measured, if at all, in different dimensions. Three types of theory in the field of learning satisfy this definition. The most characteristic is to be found in the field of physiological psychology. We are all familiar with the changes that are supposed to take place in the nervous system when an organism learns. 1 Address of the president, Midwestern Psychological Association, Chicago, Illinois, May, 1949. Synaptic connections are made or broken, electrical fields are disrupted or reorganized, concentrations of ions are built up or allowed to diffuse away, and so on. In the science of neurophysiology statements of this sort are not necessarily theories in the present sense. ' But in a science of behavior, where we are concerned with whether or not an organism secretes saliva when a bell rings, or jumps toward a gray triangle, or says bik when a cards reads tuz, or loves someone who resembles his mother, all statements about the nervous system are theories in the sense that they are not expressed in the same terms and could not be confirmed with the same methods of observation as the facts for which they are said to account. A second type of learning theory is in practice not far from the physiological, although there is less agreement about the method of direct observation, Theories of this type have always dominated the field of human behavior. They consist of references to mental events, as in saying that an organism, learns to behave in a certain way because it finds something pleasant or because it expects something to happen. To the mentalistic psychologist these explanatory events are no more theoretical than synaptic connections to the neurophysiologist, but in a science of behavior they are theories because the methods