Fixed-interval schedules of electric shock presentation: extinction and recovery of performance under different shock intensities and fixed-interval durations.
Even painful events can reinforce behavior when they arrive on fixed-interval schedules.
01Research in Context
What this study did
Zimmerman (1969) tested electric shock as a reinforcer. The shock came only after the animal pressed a lever. The time between shocks stayed the same — a fixed-interval schedule.
The team raised shock strength and also stretched the interval. They watched how fast the animal responded.
What they found
Stronger shocks made the animal press faster. Longer intervals made it press slower. The animal still showed the classic scallop: slow after shock, fast before the next one.
Even pain can keep a habit alive if the schedule is right.
How this fits with other research
Kelleher et al. (1969) got the same scallop with a shock-postponement rule. Both papers show the schedule shape, not the shock, drives the pattern.
Hymowitz (1976) added a warning light. The light cut response loss only when the schedule switched between light and no-light periods. This extends W’s work: signals matter only if they gain control through clear contrasts.
Okouchi (2003) later showed that past interval lengths still guide today’s speed. That successor study updates W by proving interval history lingers in the animal’s timing.
Why it matters
Your client may keep a problem behavior even when the payoff hurts. Check the schedule, not just the payoff. A long wait plus any reliable cue can lock the pattern in place. Thin the schedule or add a competing cue to break the scallop.
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Join Free →Plot the minute-by-minute rate of the problem act; if you see a scallop, stretch the interval before the next possible payoff.
02At a glance
03Original abstract
In squirrel monkeys responding under a schedule in which responding postponed the delivery of electric shock, the presentation of response-dependent shock under a fixed-interval (FI) schedule increased the rate of responding. When the schedule of shock-postponement was eliminated, so that the only shocks delivered were those produced by responses under the FI schedule, a pattern of positively accelerated responding developed and was maintained over an extended period. When responses did not produce shocks (extinction), responding decreased. When shocks were again presented under the FI schedule, the previous pattern of responding quickly redeveloped. In general, response rates were directly related to the intensity of the shock presented, and inversely related to the duration of the fixed-interval. These results raise fundamental questions about the traditional classification of stimuli as reinforcers or punishers. The basic similarities among FI schedules of food presentation, shock termination, and shock presentation strengthen the conclusion that the schedule under which an event is presented and the characteristics of the behavior at the time the event is presented, are of overriding importance in determining the effect of that event on behavior.
Journal of the experimental analysis of behavior, 1969 · doi:10.1901/jeab.1969.12-301