Fig. 2.

Example index and middle finger movement paths during proprioception tasks generated by the FINGER robot. FINGER moved participants’ index and middle fingers in opposing directions to create crisscross motions. One crossover event occurred during each crisscross movement wherein the index and middle fingers were directly overlapping. The position in space where the crossover event occurred varied for each crisscross movement; to create this effect, the fingers alternated between symmetric and asymmetric movements. Each crisscross movement occurred over 5 seconds, followed by a pseudo-random 0-3 second pause. During the pause, index and middle fingers were separated at 30% of the ROM by FINGER. Varying finger velocity profiles and pseudo-random pause times created non-periodic crisscross movements that participants could not predict using timing strategies