Chaining and secondary reinforcement based on escape from shock.

Three white rats were trained to press a bar while being shocked. This produced a white noise. After 30 sec they were allowed to terminate both the shock and the noise by nosing a pigeon key. Comparison of the rates of pressing before and after the onset of the noise indicated that the noise itself was the immediate reinforcing agent for pressing. Furthermore, control tests showed that pressing was maintained only if it produced the noise: either omission of the noise or elimination of the dependency of the noise on the occurrence of the response led to a gradual abolition of pressing. When automatic termination of the shock was substituted for the key nosing requirement, however, only the key nosing extinguished. This indicated that the effectiveness of the noise as a reinforcer did not depend on its status as a discriminative stimulus for some other form of operant behavior.