Figure 3. Unimanual noise patterns. A, SD of force as a function of direction of force, measured at magnitudes of 10, 15, and 20N, for each arm and each group. Right subplot, SD of force as a function of force for the dominant (Dom) and the nondominant arm (NonD). This subplot was generated by collapsing the data for each subject across all directions and then combining the two groups. B, Signal-dependent noise, measured as the slope of SD of force versus force magnitude, at each direction. Left column, This noise is plotted in Cartesian coordinates of force. Right column, The noise is plotted in joint coordinates of torque. SF, Shoulder flexion torque; EF, elbow flexion torque; SE, shoulder extension torque; EE, elbow extension torque. C, Left plot, Signal-dependent noise for each arm, averaged across all directions. Laterality index refers to the difference between signal-dependent noise produced by the right and left arms, divided by the sum of two arms. Data are mean ± SEM.