Throwing good effort after bad: Evidence for a sunk-cost effect in cognitive effort-based decision-making

The sunk-cost effect, an influential decision-making bias elicited by the consideration of past, irrecoverable resource investments toward a choice option, is well-documented for economic decisions. Contrary, evidence for sunk-cost effects for non-monetary costs, such as cognitive effort, has been mixed. Here, we present findings from two experiments in self-reported healthy adults (Exp.1 in-person, n = 36; Exp.2 online, n = 89), in which participants performed an effort investment task designed to assess the impact of past effort exertion on current choices about continuing or abandoning a course of action. Across both experiments, we found that prior resource investment substantially increased participants' willingness to invest further resources (i.e., to exert additional cognitive effort). Moreover, when current choices required higher additional effort exertion, participants were more likely to continue a course of action following larger versus smaller prior effort investments. These findings provide compelling evidence for the existence of an effort-based sunk-cost effect. Further, they highlight the importance of previous effort investments for influencing present choice behavior, indicating the need to refine contemporary cost-benefit models of effort to account for past effort exertion.