Timeout induced by differential-reinforcement-of-low-rate schedules

Three rats pressed a lever for food on differential-reinforcement-of-low-rate (DRL) schedules ranging from 16 s to 96 s. During DRL performance, a response to a second lever turned off chamber illumination and produced a timeout period during which food could not be obtained. During timeout periods, a response to the second lever reinstated the DRL schedule and associated chamber illumination. The percentage of session time spent in timeout periods increased as the DRL schedule was lengthened and decreased when the schedule was shortened. Changes in timeout percentage were primarily due to changes in the mean time per timeout rather than to changes in the rate of initiation of timeout periods. Extinction increased the timeout percentage. Elimination of the timeout contingency decreased the response rate to the timeout lever, but did not systematically affect DRL lever pressing. The rate of reinforcement appeared to be a primary determinant of the percent of session time spent in timeout periods.