1 2 Title : Task goals influence online corrections and adaptation of reaching movements 3 4 5 6

32 33 Everyday movements often have multiple solutions. Many of these solutions arise from biomechanical 34 redundancies. Often, however, the goal does not require a unique movement. To examine how people 35 exploit task-related redundancy, participants produced three-dimensional reaching movements, moving 36 to one of two rectangular targets that were diagonally oriented in the frontal (X, Y) plane. On most 37 trials, the movement was perturbed by a vertical, velocity-dependent force. Since participants were 38 free to move in 3D space, online corrections could involve movement along the perturbed, vertical 39 dimension, as well as the non-perturbed, horizontal dimension. If the motor system exploits task 40 redundancies, then corrections along the horizontal dimension should depend on the orientation of the 41 target. Consistent with this prediction, participants modified both the horizontal and vertical 42 coordinates of the trajectory over the course of learning, and the horizontal component was sensitive to 43 the orientation of the target. Furthermore, participants produced online corrections with a horizontal 44 component that brought the hand closer to the target. These results suggest that we not only correct for 45 mismatches between expected and experienced forces, but also exploit task-specific redundancies to 46 efficiently improve performance. 47