Behavioral definition of minimal reaction time in monkeys.
Tightening the reward window can push monkey release speed only to 180 ms; below that, variability explodes.
01Research in Context
What this study did
Researchers shaped key-release speed in monkeys. They used a moving payoff band. If the monkey let go within the band, it got food.
The band started wide, then got narrower. Each session demanded faster releases. The team tracked median latency and variability.
What they found
Monkeys settled at 180 ms with tiny variability. That looked like a hard floor.
When the band moved below 180 ms, spread shot up. Fast releases became erratic. The data fit a foreperiod-estimation model.
How this fits with other research
Lovitt et al. (1970) also worked with monkeys pressing bars. They showed that one monkey's rate can control another's. Both studies prove monkey operant labs give clean timing data.
LeFrancois et al. (1993) refined timing theory by adding a 'transition-lag' term. Their math predicts the 180 ms floor Wright (1972) found. Theory and experiment now match.
Baum (2021) says behavior is continuous, not discrete. A's fine-grain latency plot backs this view. Micro-second structure matters as much as total responses.
Why it matters
If you shape speed with clients, watch the variability window. When latencies stop stabilizing, the payoff window may be too tight. Back up a step, widen the band, and let the behavior settle before pushing again.
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Graph your learner's latency and its standard deviation; if spread jumps, widen the reinforcement window for two sessions.
02At a glance
03Original abstract
Two monkeys (Macaca mulatta) were trained to press a key after onset of a tone and to release it after a 1-sec fixed foreperiod terminated by a light. The effects of imposing temporal contingencies on key release reaction times were determined by reinforcing only those releases whose latencies from the light fell within a "payoff band", two time limits 50 msec apart located at some delay following the light. Over several days this delay was first gradually decreased, shortening the interval between light and payoff band, and then gradually increased again. For each delay, the median reaction time and a measure of variability were obtained from the latency distribution. For both animals, median latency could be decreased to 180 msec with the variability remaining small. Moving the payoff band still closer to the light resulted in further decrease in median latency but an abrupt increase in variability. This is in agreement with a model for simple reaction time derived from human research which suggests that this increased variability results from the inclusion of high-variability foreperiod time estimations in the latency distribution. These results indicate that interpretation of monkey response latencies as "minimal reaction times" requires examination of temporal reinforcement contingencies and variability of latencies.
Journal of the experimental analysis of behavior, 1972 · doi:10.1901/jeab.1972.18-87