Fig. 1.
Experimental apparatus. A: subject sits with right arm supported over glass surface and looks in the mirror, which reflects the computer display (LCD). The upper arm magnetic sensor is visible. B: side view of apparatus. Arm is strapped to sled, which glides on air jets. Not visible: hand (wrapped in splint to prevent wrist motion); forearm sensor (attached to bottom of air-sled); magnetic transmitter (below table). C: task workspace, showing start circle (filled circle) and target locations (open circles) in experiment 1. Thick circles, targets in training directions (θ1, θ2), for which endpoint feedback was provided. Thin circles, probe targets (no feedback). Target diameter, 2 cm; distance from start circle to probe targets, 10 cm.