Eccentric head positions bias random generation of leftward and rightward handle-bar rotations

We explored the effects of eccentric head positions on rapid rotations of a handle-bar in a modified randomization task. Subjects had to generate a random sequence of leftward and rightward handle-bar rotations; each pre-selected rotation was produced in response to a visual signal as rapidly as possible. Eccentric head positions induced a bias in that handle-bar rotations in the direction of the eccentric head position were chosen more frequently than handle-bar rotations in the opposite direction. This is consistent with previous evidence on a spatial coupling. In contrast to response selection, response initiation was not affected by eccentric head positions. The kinematic characteristics, however, differed: rotations in the direction of the eccentric head position were of larger amplitude and longer duration than rotations in the opposite direction. This difference may have been secondary to a difference in the start positions of the handle-bar, which were shifted in the direction opposite to the eccentric head position.