Relations among cognitive effort, physical effort, and delay discounting

The immediacy of a consequence and the effort required to achieve it are two key factors that influence decision making. In the current study, 170 participants completed two computer tasks to earn points. Both tasks arranged a Fixed-Interval 24-s schedule for a larger number of points, but participants could defect to a smaller immediate reward after various delays on most trials. One task required physical effort (precise clicking with the mouse), the other assessed cognitive effort (simple mathematical problems). Two levels of response difficulty were arranged in each task. There were significant effects of delay and effort for both tasks. Participants chose the larger later reward more often when the opportunity to defect was more delayed and when response effort was lower. There was no significant correlation between individuals’ reinforcer discounting due to delay and due to response effort. There were, however, significant correlations between individuals’ discounting of physical and cognitive effort suggesting effort discounting is more trait-like. The combination of delay and effort should be considered in designing tasks for educational or workplace settings.