Key‐pressing responses in the cat were maintained under conditions in which brief electric shock was first postponed by responses (avoidance), then periodically presented independently of responses, and finally produced by responses on a fixed‐interval schedule of 15 min (FI 15‐min). A steady rate of responding occurred under shock avoidance and under response‐independent shock; positively accelerated responding was engendered by the FI 15‐min schedule. A second experiment studied responding under second‐order schedules composed of three FI 5‐min components. Responding was suppressed when a stimulus was presented briefly at completion of each FI 5‐min component and a shock followed the brief stimulus at completion of the third component. Responding was maintained when each of the first two components was completed either with or without presentation of a brief stimulus and a shock alone was presented at completion of the third FI