OPERANT CONTROL OF RESPONSE LATENCY IN MONKEY: PERIPHERAL VS CENTRAL EXPLANATIONS.
PSYCHOPHYSICS LAB UNIV OF WASHINGTON SEATTLE
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Two monkeys were trained to press a telegraph key in response to a tone and release it quickly to a subsequent light or click stimulus occurring after a variable interval. After training with a self-adjusting limited hold, minimum reaction time to click was 160 msec. and to light about 200. Temporal contingencies or payoff bands were then introduced which reinforced only latencies falling between two limits 50 msec. apart. Feedback was given as to whether the response latencies were too slow, on target, or too fast relative to the payoff band. A trained animal could precisely center his latency distribution on any 50-msec.-wide payoff band located from 200 to 600 msec. after the stimulus, with from 60 to 80 of his response latencies achieving reinforcement. Distribution statistics were comparable to those of trained human subjects. Because such precise timing might be accomplished by peripheral adjustment such as changing manner of holding key, latency of EMG activation was measured in participating arm muscles. EMG activation preceded key release by a constant interval, regardless of response latency, indicating a more central mechanism for timing of brief intervals. Author