Reinforcement During Prolonged Activity

One of the most important questions in the study of prolonged activity concerns the constellation of reinforcing agents operative in maintaining work output. Such factors as degree of effort, motivation, and instruction may change progressively during performance. The fact that equivalent decrement frequently develops in performances which have widely different histories suggests a common source of autogenic reinforcement. Thus an individual who has been working strenuously all day on a new mathematical problem may find himself too "exhausted" to undertake a card game which he knows thoroughly and in which he normally excels.

The subject of compensatory reinforcement is packed with problems which we have as yet no adequate techniques to investigate. No one knows the relative reinforcing power of two different types of motivation or their relative persistence. The prospective investigator of these conditions is faced with an immediate dilemma. There are three possible indices of reinforcement: introspective report, overt behavior, and neural energy transformation; and their value to physiological interpretation is the exact inverse of their order of technical adequacy. Subjective report has not appreciably advanced our knowledge of the dynamics of reinforcement during work; measures of overt behavior leave much room for error in their interpretation; and the complex energy transformations incident to changes in neural reinforcement lack suitable instrumentation.

results. The initial decrements in restlessness and tonus are probably a consequence of a lack of control by the directive set over the behavior flux and of the widespread neural activity required to develop a creditable performance (warmingup process). The second group of factors may be due to the first, with increased neural activity serving to reinforce the potency of the directive set in its competition with other reaction tendencies. Long-continued activity would thus be characterized by the relative loss of dominance of the directive set and by an increase in neuromuscular reinforcement necessary to balance the competition of stronger and incompatible tendencies.

Work decrement is greatest when restlessness is most pronounced and least when the tonus increments are most extensive. Subject L, who showed the least work decrement, had the highest average tonus; and there was also a marked tendency for restlessness to be greatest when work decrement was most rapid. Thus it seems probable that restlessness is more indicative of loss of control, and tonus more indicative of attempted reinforcement.

The connection between restlessness and lack of control is fairly clear. Two of the main features of disturbance in a welladapted act are the presence of unnecessary and accessory movements and variability in performance. Both of these features are suggested in the records of restlessness. Not only was there an increase in the number of slight postural shifts, but their variability also increased with time. The running commentary of the subjects indicated that the majority of such movements were incidental to the performance.

Does an increase in neural activity always work to compensate for the apparent work decrement? Whether a given neuromuscular process will reinforce or inhibit depends especially upon the pattern with which it becomes incorporated. Reinforcement appears to be chiefly automatic. Subjects do not usually attempt to reinforce by voluntary contraction of any part of the musculature; but experimenters frequently note significant behavior, such as gritting the teeth, clenching the fist, or biting the lip. The question of possible reinforcement is very important to any study of continuous work; and until more crucial information is available, we may be guided by two heuristic principles. The first of these proposes that while reinforcement may be derived from the activity of any part of the neuromuscular system, the pattern will presumably vary with the performance under survey. For example, continuous writing is more likely to involve increased activity of arm muscles than of leg muscles. The second principle suggests that after a time the focus or center of reinforcing activity will shift from muscles immediately concerned in the task to more remotely concerned groups.