The effect of changes in criterion value on differential reinforcement of low rate schedule performance

The differential reinforcement of low rate (DRL) schedule is commonly used to assess impulsivity, hyperactivity, and the cognitive effects of pharmacological treatments on performance. A DRL schedule requires subjects to wait a certain minimum amount of time between successive responses to receive reinforcement. The DRL criterion value, which specifies the minimum wait time between responses, is often shifted towards increasingly longer values over the course of training. However, the process invoked by shifting DRL values is poorly understood. Experiment 1 compared performance on a DRL 30-s schedule versus a DRL 15-s schedule that was later shifted to a DRL 30-s schedule. Dependent measures assessing interresponse time (IRT) production and reward-earning efficiency showed significant detrimental effects following a DRL schedule transition in comparison with the performance on a maintained DRL 30-s schedule. Experiments 2a and 2b assessed the effects of small incremental changes vs. a sudden large shift in the DRL criterion on performance. The incremental changes produced little to no disruption in performance compared to a sudden large shift. The results indicate that the common practice of incrementing the DRL criterion over sessions may be an inefficient means of training stable DRL performance.