Evidence for separate processes underlying movement and decision vigor in a reward-oriented task

Abstract

The vigor of movement and decision-making is fundamental to many reward-oriented behaviors. While some theories propose that movement and decision are jointly invigorated to maximize a global utility (e.g., mixing reward, effort, and time), alternative perspectives suggest that the brain can separately invigorate them when advantageous. We tested these competing hypotheses using a foraging-like task that allowed experimentally assessing the vigor of movement (reaching to reward location) and that of decision-making (harvesting reward). By using a block-wise design, we measured the effects of independent manipulations of time and effort on reach and harvest durations. Decoupled effects were found on reach and harvest durations, with no inter-individual consistency between them. A model allowing separate, yet inter-dependent, optimizations of movement and decision vigor based on distinct time costs sensitive to recent temporal history predicted these results more accurately than a global utility model. These findings indicate that movement and decision vigor may flexibly depend on whether shared versus distinct time costs underlie behavior; co-regulation would arise when the vigor of movement and decision is governed by a shared time cost but decoupling may emerge when relevant for the task. Significance statementCoordinating movement and decision-making is fundamental to many reward-oriented behaviors. Current theories suggest that the brain may invigorate behavior by co-regulating movement and decision, but some experimental findings rather point to a decoupling. To shed new light on this debate, we developed a foraging-like task promoting independent and comparable manipulation of time and effort. We show that movement and decision are mostly decoupled in this task, invigorated by distinct time-cost signals. Previously experienced delays tend to amplify these time costs, thereby exerting a strong influence on behavior and indirectly linking movement and decision. Co-regulation or decoupling may hinge on whether movement and decision vigor relies on shared or distinct time-cost signals.