Sinusoidal target movements with increasing bandwidth were used to examine the breakdown of predictive tracking. Three types of instructions were given to 10 subjects: Tracking naturally with gaze and arm (gaze tracking, GT), tracking with eyes and arm (head fixated, eye-tracking, ET) and tracking with head and arm (head-tracking, HT). Maxima of the cross-correlation-functions yielded the latencies of the movement-velocities, spectra the frequency-content.

Spectra of all tracking systems showed a stronger participation of higher frequency-components in the responses. Latencies of all tracking systems increased with growing complexity of target movement in a similar manner up to 100 ms until the highest frequency component passed 0.8 Hz. More complex target movements yielded growing latencies of arm- and head-velocities (up to 400 ms, with strong correlation), but nearly constant latencies of eye- and gaze-velocities (at about 100 ms) in GT and ET.

The linear growth of arm- and head-latencies with decreasing predictability of target-movement could be due to the relatively big mechanical inertia of these systems. Where these effects are small, similarities in the way prediction works point to common stages of information processing.

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