Schedule-induced defecation.
Fixed 30-second food schedules can make rats defecate on cue—check for similar side effects in your learners.
01Research in Context
What this study did
Rayfield et al. (1982) watched rats during food sessions. They used three 32-second schedules: fixed-interval, variable-interval, and fixed-time. They counted how often the rats defecated.
Shorter fixed-interval and ratio schedules were also tested. The goal was to see if the timing of food could make bowel movements go up or down.
What they found
The 32-second schedules tripled or quadrupled defecation. Shorter intervals and ratio schedules did almost nothing.
The result showed defecation is not random stress. It is schedule-bound, just like drinking or wheel running.
How this fits with other research
Falk (1966) first saw schedule-induced polydipsia—rats drank gallons under similar timing. Rayfield et al. (1982) now prove the same rule works for a new body system.
Wilson et al. (1987) later showed satiated rats over-eat on these schedules. Together the three papers form a family: food timing can crank up water, feces, or food intake.
Morris et al. (1982), also in 1982, argued drinking is not elicited by food cues but by behavioral competition. The defecation data line up: output rises only when the schedule lets other behaviors compete for time.
Why it matters
If you run FI 30-s or VI 30-s reinforcement with clients, watch for extra bathroom trips. The bowel may follow the schedule, not illness. Adjust timing or add breaks to keep side effects low.
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02At a glance
03Original abstract
Excessive defecation, typically considered to be a concomitant of stress, was experimentally induced or eliminated under specific schedules of positive reinforcement of lever pressing by rats. The schedules were, by and large, those under which polydipsia is typically induced. In the first of three experiments, rats under fixed-interval 32-second schedules and variable interval 32-second schedules for food and water reinforcers defecated profusely, but not under fixed-interval one-second schedules or other small interval schedules. Somewhat higher rates of defecation were observed on variable interval 32-second schedules than on fixed-interval 32-second schedules. In a second experiment, fixed-ratio schedules were used, some of which resulted in responding such that reinforcement densities were similar to those on the interval schedules that induced defecation. Defecation was not systematically induced by these ratio schedules. In a third experiment, fixed-time schedules of food presentations were utilized. High rates of defecation were induced comparable to those induced by interval schedules of the same time parameter. No other behavior commonly termed "emotional" was observed in any of these experiments.
Journal of the experimental analysis of behavior, 1982 · doi:10.1901/jeab.1982.38-19