Abstract
Previous research has shown that humans are able to select movements that achieve their goal while avoiding negative outcomes by selecting an 'optimal movement endpoint' which is modeled based on the participants' endpoint variability and the payoffs associated with the environment. Although in daily interactions the values associated with our goals vary on a moment-to-moment basis, our ability to adapt endpoint selection to changing payoffs in lab-based tasks has only been examined across blocks of trials. The purpose of the present study was to determine whether participants could adjust their endpoint when parameters of the model changed trial-to-trial. Participants aimed to a target circle that was overlapped by a penalty circle. They received 100 points for hitting the target and lost points for hitting the penalty area. The magnitude of the penalty or the distance between the centers of the circles was changed randomly in separate blocks of trials. We found that participants shifted their endpoint when the distance between the circles was varied, but not when the value of the penalty circle was varied. We suggest that participants are more optimal with changing distance parameters because the distance between the two circles is an intrinsic property of the visual stimuli. The results of the Penalty block suggest participants in previous studies needed to receive performance feedback from earlier trials in order to aim to an optimal mean endpoint.Acknowledgments: This research was supported through grants from the Natural Sciences and Engineering Research Council of Canada and the Ontario Ministry of Research and Innovation.