Neural basis of the undermining effect of monetary reward on intrinsic motivation

Abstract

Contrary to the widespread belief that people are positively motivated by reward incentives, some studies have shown that performance-based extrinsic reward can actually undermine a person's intrinsic motivation to engage in a task. This "undermining effect" has timely practical implications, given the burgeoning of performance-based incentive systems in contemporary society. It also presents a theoretical challenge for economic and reinforcement learning theories, which tend to assume that monetary incentives monotonically increase motivation. Despite the practical and theoretical importance of this provocative phenomenon, however, little is known about its neural basis. Herein we induced the behavioral undermining effect using a newly developed task, and we tracked its neural correlates using functional MRI. Our results show that performance-based monetary reward indeed undermines intrinsic motivation, as assessed by the number of voluntary engagements in the task. We found that activity in the anterior striatum and the prefrontal areas decreased along with this behavioral undermining effect. These findings suggest that the corticobasal ganglia valuation system underlies the undermining effect through the integration of extrinsic reward value and intrinsic task value.crowding-out effect | dopamine | midbrain | neuroeconomics P erformance-based incentive systems have long been part of the currency of schools and workplaces. This predominance of incentive systems may reflect a widespread cultural belief that performance-based reward is a reliable and effective way to enhance motivation in students and workers. However, classic psychological experiments have repeatedly revealed that performance-based reward can also undermine people's intrinsic motivation (1-6), that is, motivation to voluntarily engage in a task for the inherent pleasure and satisfaction derived from the task itself (3-5). In a typical experiment of this "undermining effect" [also called the "motivation crowding-out effect" (7-9) or "overjustification effect" (2)], participants are randomly divided into a performance-based reward group and a control group, and both groups work on an interesting task. Participants in the performance-based reward group obtain (or expect) reward contingent on their performance, whereas participants in the control group do not. After the session, participants are left to engage in any activity, including more of the target task if they wish, for a brief period when they believe they are no longer being observed (i.e., "free-choice period"). A number of studies (4-6) found that the performance-based reward group spends significantly less time than the control group engaging in the target activity during the free-choice period, providing evidence that the performance-based reward undermines voluntary engagement in the task (i.e., intrinsic motivation for the task).The undermining effect challenges normative economic theories, which assume that raising monetary incentives monotonically increases motivation and, more im...

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