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

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 that separately optimized movement and decision vigor predicted these results better than a global utility model. These findings support the separate control hypothesis, indicating that distinct time-cost signals (sensitive to recent temporal history) may invigorate movement and decision. We conclude that movement and decision vigor is only indirectly linked, with any apparent co-regulation arising when both are governed by a shared temporal signal reflecting a common cost of time.