Schedule-induced defecation: No-food and massed-food baselines.

Defecation rate was monitored during daily 30-min periods as 16 rats were exposed to different sequences of the following three experimental conditions: (a) a fixed-time 60-s food delivery schedule, (b) a massed-food presentation baseline, and/or (c) a no-food baseline. All food delivery was response independent. Rate of defecation increased during fixed-time 60-s food delivery when compared to baseline rates of defecation established during no-food and massed-food baselines. This effect was present for 12 of 16 rats during four alternative sequences of experimental conditions. Within-subject reversals established reliability of this effect. Schedule induction of defecation is clearly demonstrated under these conditions.