Effort can have positive, negative, and non-monotonic impacts on outcome value in economic choice

Every action demands some effort, and its level influences decision-making. Existing data suggest that in some decision contexts effort devalues outcomes, but in other contexts effort enhances outcome valuation. Here, we describe an empirical study and propose a model that incorporates negative, positive and mixed impacts of effort on outcomes in different decision contexts and in different participants. Participants chose between money and an item associated with varying levels of stair climbing effort. Some participants had previous direct experience with a real physical effort and made decisions about a physically present reward. For other participants, the effort and the associated reward was always purely hypothetical. Furthermore, the decisions were framed as prospective or retrospective – before or after effort exertion. The key behavioral finding was that in the “real” condition, greater effort decreased outcome value when considered prospectively, but increased outcome value when considered retrospectively. Interestingly, even within the same decision context, individuals showed diverse relationships between effort and outcome value. These relationships ranged from those where greater effort increased value, decreased value, to non-linear patterns, where small effort initially increased outcome value but higher effort decreased it, or the other way around (initial decrease followed by a decrease). When our model was applied to participants’ individual choices, it was able to capture the monotonic and non-monotonic relationships and outperformed previous solutions.