Objective variables of the predictable tracking task. (A) Coefficient of determination of user motion trajectory. Bold lined waveform, user motion signal; thin line, reference waveform for a manipulation task. (B) Temporal accuracy. Bold lined waveform in the top plot, reference waveform; light shading, user motion signal for a manipulation task. A maximum and minimum point on the up and down cycles of the user signal is shown. The time taken to reach maximum and minimum points for each movement cycle is compared between the two signals. (C) Amplitude consistency. An arbitrary line drawn on a user motion signal represents amplitude consistency in upward and downward directions.