Fixed Ratio Schedule Responding as a Function of Contingency Descriptions and Reinforcement Delay

15 human Ss received alternating sequences of 0- and variable 15-sec. delay of reinforcement on a FR 15 schedule lever-pulling task. Groups of 5 Ss received either rate instructions to maximize reinforcement or correct responses, or no instructions. Results indicate that delay of reinforcement reduced response rates only for Ss with rate instructions.