The effects of punishment intensity on squirrel monkeys.
Shock strength tunes punishment like a dial, and past settings shape how fast behavior returns.
01Research in Context
What this study did
Four squirrel monkeys pressed a lever for food on a VI schedule.
The team added mild electric shocks that grew stronger in steps.
They watched how each new shock level changed the monkeys’ lever pressing.
What they found
Higher shocks cut responding in smooth, step-wise fashion.
When shocks dropped back down, recovery matched the last suppression level.
Behavior kept a ‘memory’ of the prior shock strength.
How this fits with other research
McKearney (1970) saw the same graded pattern in pigeons under multiple schedules, showing the idea crosses species and schedules.
Kruper (1968) later found punishment cut rates by the same percent no matter how rich the food schedule was, building on the orderly suppression F et al. first mapped.
Thomas et al. (1968) used the same monkeys and shock steps but measured biting attack instead of lever pressing; attack rose as shocks got stronger, the mirror image of the response drop seen here.
Why it matters
Punishment does not work like an on-off switch; it dims behavior in proportion to its strength. When you thin or remove punishment, expect recovery to match the last suppression level, not the starting point. Start low and move up only as needed, and track past intensities to predict bounce-back.
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02At a glance
03Original abstract
Responses of squirrel monkeys were maintained by a variable-interval schedule of food reinforcement. Concurrently, punishment consisting of a brief electric shock followed each response. As has been found for pigeons and rats, punishment did not produce extreme, all-or-none reactions. By gradually increasing the punishment intensity it was possible to produce response rates intermediate to no suppression and complete suppression. Similarly, the moment-to-moment response rate was free of extreme fluctuations. A "warm-up" effect occurred in which the punished responses were especially suppressed during the initial part of a session. The pre-punishment performance was negatively accelerated within a session, and punishment reduced the degree of negative acceleration. When punishment was discontinued, responding recovered immediately except when suppression had been complete or prolonged. When the punishment intensity was decreased gradually, more suppression resulted at a given intensity than when intensity was increased gradually. This suggests a "behavioral inertia" effect wherein behavior at a new punishment intensity is biased toward the behavior at the previous value. A corollary generalization is that the larger the change in intensity, the less the behavior at the new value will be biased toward the behavior at the previous value.
Journal of the experimental analysis of behavior, 1967 · doi:10.1901/jeab.1967.10-95