Aiming at extending previous findings on perceptuo-motor control of interceptive actions, this project has the purpose of evaluating (a) the effect of expectancy, and (b) uncertainty on performance of interception. The study will be conducted through two experiments, in which participants will intercept a moving virtual target with their preferred arm, having their movements filmed for analysis. In Experiment 1 the effect of expectancy on target velocity will be investigated. For such, a group will have practice in the interceptive action under constant velocity while another group will practice the task with target velocity decrease during the target displacement. In the following phase, both groups will be tested in a situation of 50% of chance of target moving at a constant velocity, and 50% of chance of velocity decrease during target motion. Experiment 2 is organized with the purpose of assessing the effect of uncertainty about target velocity. In this investigation conditions of constant velocity in a block of trials (low contextual interference) and random variability of target velocity (high contextual interference) will be compared. In both experiments temporal error and kinematic variables related to the temporal organization of the movements will be evaluated. The main hypothesis is that the expectancy (internal model) overlaps on visual information for control of this task.
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