Figure 6. Experimental setup, the robotic arm (HapticMaster), rear-projection screen, and a subject sitting on a chair, while holding the manipulandum of the robotic arm.

The task instruction was to move the ball-and-cup object rhythmically between the two green targets at a frequency of 1 Hz. As long as the excursion maxima alternated between the wide target regions, the task was satisfied. Hence, the subjects could choose their movement amplitude.