Reward-based motor adaptation can generalize across actions

Recently it has been shown that rewarded variability can be used to adapt visuomotor behavior. However, its relevance seems limited because adaptation to binary rewards has been demonstrated only when the same movement is repeated throughout the experiment. We therefore investigated whether the adaptation is action-specific and whether the amount of exploration depends on spatial complexity. Participants pointed to 3-D visual targets without seeing their hand and could use only binary reward feedback to adapt their movements. We varied the number of target positions and the number of dimensions the feedback was based on. Because the feedback was based on a 5-cm rightward shifted hand position, adaptation was needed for good performance. The participants started naïve to the perturbation. If actions were made toward a single target position and the feedback was based on the lateral component of their response only, participants adapted completely within 200 trials. Having more than 1 target position or more than 1 dimension of performance resulted in considerably less adaptation but did not affect the exploration. Thus, reward-based adaptation can generalize across actions but is reduced by spatial complexity, whereas exploration is not affected by spatial complexity.