Some effects of the conditioned suppression paradigm on operant discrimination performance.

Three experiments were conducted with rats to determine the effects of electric shock on responding during an operant discrimination. In two of these experiments, a conditioned suppression procedure was superimposed upon a stimulus signalling the availability of food reinforcement (S(D)). Response rates were greatly suppressed, not only in the warning signal periods which preceded each shock, but in the presence of S(D), and the stimulus signalling the unavailability of reinforcement (S(Delta)) as well. A third experiment, in which a very mild shock was used without a warning signal, demonstrated an increased response rate in S(D) and S(Delta), although this effect was rather unsystematic. In a similar study, Hearst (1965) found an increased rate in S(Delta) independent of any change in the S(D) rate. The present study failed to obtain Hearst's effect but illustrated a suppressive effect with a similar procedure.