Working harder for less: effect of incentive value on force of instrumental response in humans

The present article reports evidence from human subjects that high payoff for instrumental performance may cause reduced vigour of response compared to the vigour observed for lower payoffs. Vigour of response, as measured by force of pressing (Experiment 1) and number of fortune wheel turns (Experiment 2), was inversely related to payoffs, with higher vigour in the low payoff conditions. Experiment 2 further demonstrated this effect, regardless of whether or not payoff depended on performance. These findings are related to parallel animal data, and an analysis in terms of a learned incentive-effort hypothesis is offered. Experiment 3 presented support for this hypothesis. The results are argued to be of importance to the understanding of how reinforcers affect human instrumental performance.