Impact of decision and action outcomes on subsequent decision and action behaviors in humans.

Speed-accuracy tradeoff adjustments in decision-making have been mainly studied separately from those in motor control. In the wild however, animals coordinate their decision and action, often deciding while acting. Recent behavioral studies support this view, indicating that animals, including humans, trade decision time for movement time to maximize their global rate of reward during experimental sessions. Besides, it is well established that choice outcomes impact subsequent decisions. Crucially though, whether and how a decision outcome also influences the subsequent motor performance, and whether and how the outcome of a movement influences the next decision is unclear. Here we address these questions by analyzing trial-to-trial changes of choice and motor behaviors in healthy human participants instructed to perform successive perceptual decisions expressed with reaching movements whose duration was either weakly or strongly constrained in separate tasks. Results indicate that after a wrong decision, subjects who were weakly constrained in their action duration decided more slowly and more accurately. Interestingly, they also shortened their subsequent movement duration by moving faster. Conversely, we found that errors of constrained movements not only influenced the speed and the amplitude of the following movement, but those of the decision too. If the movement had to be slowed down, the decision that precedes that movement was accelerated, and vice versa. Together, these results indicate that from one trial to the next, humans seek to determine a behavioral duration as a whole instead of optimizing each of the decision and action speed-accuracy trade-offs independently of each other.