Neuromuscular Antecedents of Variable Reaction

At any given moment the organism is exposed to a great mass of internal and external excitants. If each of these excitants were connected with its own private motor mechanism, it would be theoretically possible for each to effect its response individually. But, as we have seen, afferent channels are five times as numerous as efferent channels; and central nervous organization is such that all afferent nerves share the control of the entire motor mechanism. Consequently, without some internal regulation there would be an indiscriminate diffusion of the motor discharge through all the effectors. This regulation is provided by a narrowing of the afferent flux into prepared adjustor and effector channels. That psychologists have long recognized this selective feature of neuromuscular action is indicated by their use of the terms set, einstellung, aufgabe, determining tendency, and predisposition. These terms indicate that the organism is never neutrally disposed to the various environmental agents which act upon its receptors. Instead it has various ways of taking the stimulus, ways which anticipate and determine the ultimate form which overt response will take. A man may glance and see either a duck or a rabbit, depending upon the way he is set or predisposed toward it. If he has recently been hunting waterfowl, he may react to it as duck; whereas if he is a pet fancier, the rabbit predisposition may be paramount. Similarly, individuals will react differently to a wooded park according to their particular "thought set." The realty agent will see it as a possible subdivision, the nature lover as a bit of woodland to be preserved intact at all odds, and the entomologist as a breeding place for mosquitoes. One can react to a catastrophic event which calmness instead of horror if he is properly forewarned. All complicated skills, such as typewriting, piano playing, and automobile driving, have their characteristic sets.

The importance of these antecedent neuromuscular conditions was first recognized in experiments on reaction time, in which it was found that the preliminary attunement aroused by the ready signal increased the speed of subsequent response.

The great bulk of psychological work and experimentation in the last two decades has dealt directly or indirectly with the influence of this phenomenon upon all varieties of performance. The judgment as to which of two weights is heavier results from a motor adjustment (einstellung) or tendency to expend the same amount of force in lifting the second weight as was expended in lifting the first; the response is "heavier" or "lighter" according to whether the second lifting necessitates a greater or a less expenditure of energy. The same general phenomenon appears in even subtler forms. For example, "giving attention" is essentially a matter of proper preparation. In the more complex forms of intercerebral action, bodily sets (often referred to as "conscious attitudes") inform the organism of its general position upon matters of the moment and aid in making appropriate adjustments during the progress of an involved intraneural reaction sequence. In analysis of the antecedent determinants of specific reactions, the psychologist is thus many strides ahead of the physiologist. Although considerable is known about the functional significance of various sets and their conditions of occurrence, the neural dynamics which are involved are not understood. It is possible that the term set is physiologically superfluous, and that the phenomena which it describes can be adequately explained by principles of neuromuscular action already known. However, we can use it for the time being, as does the psychologist, to describe an important class of organic variables which are partially controlled by instruction, and which exercise a selective and determining influence over subsequent responses.