An animal model of excessive eating: schedule-induced hyperphagia in food-satiated rats.
Intermittent reinforcement schedules can make full rats overeat, proving that timing alone can drive excess behavior.
01Research in Context
What this study did
Wilson et al. (1987) worked with 19 food-satiated rats.
The rats earned brain stimulation on fixed-interval or fixed-ratio schedules.
While the pulses arrived, wet mash sat freely available in the cage.
What they found
Fourteen rats ate at least one-and-a-half times their normal amount.
Eleven packed away more than 22 grams in three hours — almost half a daily ration.
The eating happened only when reinforcement was intermittent, showing schedule-induced hyperphagia.
How this fits with other research
Falk (1966) saw the same pattern with water: rats drank far more under interval food schedules.
Rayfield et al. (1982) later found the schedule even made rats defecate more.
Together the papers prove the schedule, not the reinforcer, drives the extra behavior.
PREMACK et al. (1963) also got satiated rats to over-eat, but they did it by taking away running wheels.
That study shows deprivation can spark eating; the 1987 study shows timing alone can do it.
Why it matters
If intermittent reinforcement can override fullness in rats, it can do the same in humans.
Watch for schedule-induced side effects when you thin reinforcement programs.
Check for extra snacking, drinking, or stereotypy as you move to FI or VR schedules.
If the new behavior is unsafe, add response cost or signaled delays — tactics shown by Paul et al. (1987) to cut schedule-induced drinking.
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02At a glance
03Original abstract
Nineteen rats were maintained throughout the experiment on ad libitum wet mash and water and were trained to press a lever on fixed-interval or fixed-ratio schedules of reinforcement with electrical brain stimulation. Fourteen rats ate at least 150% more mash during intermittent reinforcement sessions than during baseline, massed reinforcement control, and/or extinction sessions. In a 3-hr session, 11 of those 14 consumed more than 22 g of wet mash (13 g dry weight), the equivalent of nearly half an animal's daily food intake. In subsequent control sessions, the electrodes did not support stimulus-bound eating despite attempts to make stimulation parameters optimal. These results indicate that the eating was schedule induced or adjunctive, and suggest that the procedure may provide an animal model of excessive nonregulatory eating that contributes to obesity in humans.
Journal of the experimental analysis of behavior, 1987 · doi:10.1901/jeab.1987.47-335