CONCURRENT SCHEDULES OF PRIMARY AND CONDITIONED REINFORCEMENT IN RATS

Rats responded on a fixed‐interval schedule during which a 3‐sec stimulus preceded each water reinforcement. The stimulus was then scheduled concurrently for responses on the same lever according to either a variable interval or a variable ratio. Although water reinforcement. continued on a fixed‐interval schedule, the pattern of responding became typical of a variable‐interval or variable‐ratio schedule. When the 3‐sec stimulus was presented on a variable‐interval or variable‐ratio schedule, but was omitted on the fixed‐interval schedule, the response rate decreased. When the stimulus occurred after the same time periods as those of the variable‐interval schedule, but at least 7‐sec after the last response, the rate decreased. The rate became higher when the fixed‐interval schedule was discontinued and each presentation of the 3‐sec stimulus was followed by water on a variable‐interval schedule. When both water and the 3‐sec stimulus were discontinued for a period of time, resulting in extinction of the lever response, and the 3‐sec stimulus alone then presented on a variable‐interval or variable‐ratio schedule after lever responses, rate increased and then gradually decreased. 1969 Society for the Experimental Analysis of Behavior