Conditioned suppression of free-operant avoidance.

The responses of white rats were maintained on an unsignalled free-operant avoidance schedule. Superimposed on the avoidance schedule was a blinking white light followed immediately by response-independent electric shock. Duration of the light stimulus was either 1 or 3 min. Avoidable shock was 1.5 mA; response-independent shock was 7.5 mA. Suppression of responding during the light stimulus (both durations) developed over sessions. Responding immediately following the response-independent light-shock sequence was neither suppressed nor accelerated. The similarity is noted between the present result and findings of "positive conditioned suppression".