Periodic eye tracking in the monkey.

1. Eye movements were measured in monkeys trained for visual tracking.2. In response to periodic square wave target movements, monkeys do not show a significant reduction in the latency of saccadic movements.3. Under similar conditions, human beings subconsciously reduce their latency and after several cycles are in step with the target.4. In response to sinusoidal targets, monkeys show a latency or phase lag which increases monotonically with frequency starting at 0.3 c/s. Human beings can remain in phase with the target at frequencies up to 1.0 c/s.5. Hence, monkeys do not exhibit the human predictive tracking response.