Modifying Influence of Neuromuscular Sets

The psychophysiology of set is extremely difficult to attack experimentally. The most obvious approach is to take a definite response to a definite external stimulus and observe modifications in this response aroused by instruction. The fact that instruction exercises only a partial control over the condition of the organism prior to stimulation makes it necessary to vary the condition systematically on a background of general and variable change in order to analyze its effect.

During the performance the tension of the flexors of the arms and the legs was varied experimentally by causing each limb in turn to sustain a weight. Finger oscillation was most rapid when the experimentally induced tension was localized in the muscles near the reacting group, and least rapid when such tension was localized in an anatomically and neurologically remote group. Further work led to the suggestion that the facilitative effects of many reactions sets is due to an optimal localization of tension in the muscles which are involved in the response.

In the simple reaction time experiment various investigators have shown that the amount of pressure on the reaction key varies according to whether the subject is told to adopt a sensory set (attention on the stimulus) or a motor set (attention on the response). The motor set is expressed largely by the preliminary tonic contraction of muscles involved in the act of pressing or releasing the key. This makes for a more rapid response than does the sensory set, where the preliminary pattern of muscular contraction is more diffuse and less specifically localized.