SCHEDULE-INDUCED TIMEOUT - EFFECTS OF TIMEOUT-CONTINGENT DELAYED REINFORCEMENT

Rats' lever pressing turned off stimuli associated with various response-independent fixed-time schedules of food delivery and produced a timeout period during which food delivery could not occur. A lever press during timeout turned on the schedule-associated stimuli and reinstated the fixed-time schedule. Every response that produced timeout ended the timing of fixed time intervals; timeout terminating responses started the timing of fixed-time schedules over again. The percentage of session time spent in timeout periods generally increased as the rate of food delivery decreased. When food delivery could not occur, about half of the session time was spent in the stimulus condition formerly associated with timeout. The majority of timeout periods were initiated after 15 seconds or more had lapsed since the last food delivery. When timeout periods could not be produced, lever pressing rates either decreased or were not affected. The rate of food delivery appeared to be a primary determinant of time spent in timeout periods. The results may be inconsistent with interpretations emphasizing escape from aversive aspects of schedules of positive reinforcement.