The Notion of Drive

The majority of psychologists have felt that even on the physiological side, motivation involves something more special than a mere account of the mechanism through which the reaction is determined by the object or stimulus. Wood worth, for example, in his Dynamic Psychology, says that the mechanism shows "how" it is done, whereas for a complete motivational account we require an answer to the question as to "why" the specificity exists. Distinctions of this sort appear to be very helpful as aids to popular exposition, but they must be regarded with considerable suspicion if our purpose is to adhere strictly to scientific analysis. If we are considering the operations of a machine, such as a printing press, the question of "how" would seem to exhaust the problem so far as the inherent factors in the process are concerned. If we ask "why" the printing press acts as it does, we may mean a number of different things. In the first place, it is possible that we are interested concerning the manner in which ultimate mechanical laws control this particular device, but the answer to this would necessarily be embodied in that to the question, "how?" Secondly, we might interpret the question, "why," as a reference to the purposes or ideas of the operator, the owner, or the inventor of the machine. In this case, we should be going beyond the problem which is immediately before us, and introducing irrelevant considerations. A third interpretation might lead us to a study of the electric motors, power lines, dynamos, steam engines, and so forth, which energize the press. It is this latter meaning which seems to be paramount in the minds of such writers as Woodworth and McDougall. They feel compelled to regard the nervous mechanism as being essentially inert, requiring some outside source of power to keep it in motion.

Although this proposition may actually apply to the operations of some response mechanisms, we are by no means justified in viewing it as a general necessity. The division of a machine into inert and activating parts may be a helpful mode of analysis, but it is, nevertheless, arbitrary. If we consider a steam engine, for example, as comprised not only of so many metallic parts, but of redhot coals, boiling water and steam, then the mechanism is self-activating, and the question as to why it moves is answered by a complete analysis of its inherent nature and properties. Now the neuromuscular systems of animals appear, at least superficially, to be self-activating, or energizing devices of this sort, which may be controlled by external agencies but which do not need to draw upon the latter for power. The familiar comparison of the nerve impulse to the ignition of a train of gun-powder illustrates this principle.

In the last analysis, the notion of drive as advocated by Woodworth, McDougall and others can undoubtedly be given a distinctive interpretation, but in beginning the attack upon the problem of motivation, we cannot limit the investigation to a search for "prime movers." The question in which we are interested is the much broader one of the total structure and process which determines the specificity of response or gives rise to any observable effector reaction. However, it is certainly legitimate to add to this question the one as to the historical foundation, or origin of the structures which underlie this total structure and process. This is particularly pertinent in the case of a mechanism such as the nervous system, which is subject to significant changes at every moment throughout its existence. The answer to the question as to the origin of specific response mechanisms is another possible interpretation of the answer to the question, "why?"

Perhaps objections may be raised to these views on the ground that they unduly generalize the problem of motivation. It may be said that we can distinguish clearly even on a purely physiological basis, between pure reflexes and the more complex forms of response which are usually indicated by the term, behavior. It may be said that there is no question of motivation in a cough, but that the cigarette habit may require a motivational explanation. However, as we have already pointed out, it is hardly safe to start with distinction of this sort, since we may eventually discover that the fundamental principles which control reflexes and habits are the same, at least in part. The elimination of the simpler forms of response from the problem of motivation can really only be justified from the standpoint of a psychological definition, in which the relation to consciousness is made the determining feature.

Psychophysical Parallelism

Now, if we adhere firmly to the above conception of organisms as physical systems, it is really impossible for us to include any mental or psychical terms whatsoever in their supposed operations. However, it would be equally absurd to deny the existence of these psychical factors, since their reality is far more evident than that of the physical terms. The physical ideas are the outcome of an elaborate and frequently hazardous process of reasoning, whereas the psychological phenomena are always with us, no matter what our opportunities or capabilities may be in the domain of scientific thought. Consequently, it appears that the physical and the psychological data must be organized into logically distinct scientific systems, and that the problem of their interrelations must be considered as a third question, separate from that of the internal relationships of the terms within the two respective accounts. This method of treating the facts is given the name, psychophysical parallelism.

The parallelistic view, first proposed by Leibnitz, has been the working scheme of the majority of scientific psychologists since his time. However, it has aroused severe intellectual pains in philosophic minds, thus stimulating many a violent reaction against it. It is fundamentally opposed to the natural desire for a monistic explanation, and to the demand for continuity between processes which go on in synchronism with each other, as do those of body and mind. Behaviorists and exclusive physiologists turn their thoughts away from the mental side of the parallelism, in an endeavor to avoid recognition of its obnoxious features. Idealists and exclusive introspectionists find unity in a shut-in mentalism. Interactionists, and blurry thinkers in general, scoff at the scheme as an academic creation, and mix physical and psychological notions at random. But if we envisage all of the facts in their empirically demonstrable relationships, and in the light of the most firmly established modern theories, we cannot escape the parallelistic method. Other views lead to confusion or neglect. Nevertheless, the mystery which is generated is far from being insoluble, without entailing either of these undesirable features. Concerning such a solution, we shall have more to say later.