Figure 6

Hand paths while reaching to 24 targets in 5 locations (4 cm & 2 cm distant). The circular insets show the normalized magnitudes of gain ratios after tuning for each direction. They are plotted within a unit circle as arrows in the direction of the target from the hand. This demonstrates that gain tuning is dependent not only on target location relative to the hand, but also on the concurrent arm configuration, particularly here as the forearm approaches and crosses the horizontal line y = 12.5 cm (tangent to the elbow y-limit). Note that some trajectories are left untuned intentionally (red traces) – Figure  5 has already demonstrated that all directional motions can be tuned. Notice that these red trajectories naturally straighten or naturally become more curved as the configuration of the arm changes between target sets 1 through 5.