Testing the link between decision and action dynamics

Movement tracking is a popular behavioral process-tracing method promising real-time insights into the dynamics of human cognition. Rooted in the viewpoint of embodied cognition, the method commonly assumes a continuous link between cognitive and action dynamics. However, this assumption has never been investigated rigorously. Here we directly investigate this assumption in a dot motion task in which the dot motion is closely coupled to the movement of the mouse cursor. Hence, we paralleled the dynamics of the decision process (i.e., evidence accumulation) with the action dynamics (i.e., cursor movement). Our results show that the action dynamics accurately reflect many aspects of the decision dynamics but with little support for a continuous link. Instead, our results suggest that there is an intermittent link between decision and action dynamics, involving an additional evidence accumulation process that governs when and how cursor movements reflect evidence accumulation from dot motion. This additional process might represent a core mechanism that smooths noisy perceptual inputs with a variable window size and hence solve the cost-benefit trade-off of action in situated decision-making.