Responding in the squirrel monkey under fixed-ratio schedules of stimulus termination.
Fixed-ratio schedules can keep avoidance responding alive through pure stimulus termination, no shock-rate reduction needed.
01Research in Context
What this study did
Scientists worked with squirrel monkeys. They set up a lever-press task. Each monkey had to press the lever a fixed number of times. After the last press, a bright light and loud noise turned off. The light and noise came back on after a short break.
Shock was always possible. The key twist: the monkey got the same number of shocks no matter how fast or slow it pressed. The shock rate stayed flat across sessions.
What they found
The monkeys kept pressing. They finished every fixed-ratio (FR) requirement even though faster pressing did not cut shock. The behavior held steady for many sessions.
The result shows the simple end of the warning stimulus was enough to keep the chain going. Reducing shock was not required.
How this fits with other research
Peterson (1968) looked almost identical. That study also used squirrel monkeys and shock. It found pressing stopped once actual shock rate matched the potential rate. The two papers seem to clash, but the methods differ. Peterson (1968) let shock rate follow response rate in some phases; Zeiler (1977) locked shock rate flat from the start. The earlier paper proves shock reduction can matter; the new one proves it is not always needed.
Cullinan et al. (2001) showed extra, unearned reinforcers make rat lever pressing harder to extinguish. Both studies ask what keeps responding alive when programmed pay-offs change. Zeiler (1977) answers for negative reinforcement; Cullinan et al. (2001) answers for positive reinforcement.
Van Hemel (1973) showed monkeys press more when a stimulus gives clear information. Zeiler (1977) adds that stimulus termination alone can feed the loop even if the information does not cut harm.
Why it matters
If you run avoidance programs, do not assume the client must feel less aversive for the behavior to stick. A reliable cue that ends or removes the warning stimulus can maintain responding all by itself. Check whether your SD offset is truly contingent on the target response; that offset may be doing the heavy lifting even when rate-reduction is impossible.
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02At a glance
03Original abstract
Key pressing was maintained under a fixed-ratio schedule in which electric shock was scheduled for delivery at a fixed time (t seconds) after each stimulus onset, and every n(th) response terminated the stimulus and initiated a timeout from shock. Under this procedure, the higher the rate of responding, the briefer the duration of the stimulus presentation and the lower the frequency of shock delivery. The effects of several schedule parameters were studied to determine whether the maintenance of responding was dependent on an inverse relation between response rate and shock frequency. Shock rate and shock frequency were made independent of response rate by decreasing the value of t to 0.5 second and delivering shock only during the first presentation of the stimulus after a fixed time, including stimulus and timeout durations, had elapsed since the previous shock. The experiments showed that shock frequency and response rate are inversely related when t is of relatively long duration compared to the value of the fixed-ratio parameter, but that a decrease in shock rate or frequency due to a high rate of responding is not necessary for the maintenance of responding under a fixed-ratio schedule of stimulus termination.
Journal of the experimental analysis of behavior, 1977 · doi:10.1901/jeab.1977.27-495