Abstract
Prior knowledge about the sensory information available on an upcoming aiming trial allows performers to execute a movement that strategically utilizes this information. When prior knowledge is not provided and performers are unaware of the sensory environment they will be faced with, they typically prepare for the worst-case scenario (e.g., Hansen et al., 2006). The purpose of this study was to examine whether prior knowledge about the mass of a stylus impacted the execution of a goal-directed movement, so that the consequences of spatial variability (i.e., target relative location of primary submovement end points) could be minimized. In this case, planning for the worst-case scenario is associated with movements made with a heavier stylus, since they generally involve greater initial force requirements and higher spatial variability. Three groups of participants performed goal-directed aiming movements with a light (36g) and heavy (243g) stylus. Two groups were provided with prior knowledge about the stylus to be used on the upcoming trial and followed either a random (PK) or blocked (BL) protocol; another group was yoked (Y) to the PK group and was not provided prior knowledge. Movements with the heavy stylus were spatially more variable at the peaks of velocity and deceleration, and demonstrated greater undershoot biases with the primary submovements. However, there were no differences between groups in these measures. Therefore, independent of prior knowledge, kinematic differences in movements with the styli were suggested to be rectified online by a process of visual regulation that guided the limb onto the target.Acknowledgments: Natural Sciences and Engineering Research Council of Canada (NSERC)