Figure 3.

Trajectories before and after training. Initial trials in the 0DF, −45DF, and 80DF force fields were perturbed away from the straight path toward the target causing the hand to move outside of the safety zone (located at 5 cm to either side of the x-axis and represented by the solid back lines in the figure). Each field perturbed the arm in a slightly different direction. After training in the force fields for 75–150 trials, subjects were able to make straight (or gently curved) movements to the final target without being perturbed.