Online movements reflect ongoing deliberation

Abstract

From navigating a crowded hallway to skiing down a treacherous hill, humans are constantly making decisions while moving. Insightful past work has provided a glimpse of decision deliberation at the moment of movement onset. Yet it is unknown whether ongoing deliberation can be expressed during movement, following movement onset and prior to any decision. Here we tested the idea that an ongoing deliberation continually influences motor processes-prior to a decision-directing online movements. The deliberation process was manipulated by having humans of either sex observe tokens that moved into a left or right target. Supporting our hypothesis we found that lateral hand movements reflected deliberation, prior to a decision. We also found that a deliberation urgency signal, which more heavily weighs later evidence, was fundamental to predicting decisions and explains past movement behaviour in a new light. Our paradigm promotes the expression of ongoing deliberation through movement, providing a powerful new window to understand the interplay between decision and action.Significance Statement Simultaneously deciding and acting has been critical to our survival and undoubtedly shaped our evolution. Classic decision-making and sensorimotor paradigms do not permit or have obscured the expression of ongoing deliberation via online movement. Here we found that deliberation could be expressed via movement when the motor system was already actively engaged. By considering both urgency and evidence accumulation, often cast as competing theories, we were able to consolidate current and past decision-making and movement behaviour.