Transfer of inhibitory stimulus control in operant feature-negative discriminations

Two experiments examined transfer of stimulus control after discrete-trial operant serial (T+ /F→T—) and simultaneous (T+/FT—) feature-negative discrimination training in rats. The temporal arrangement of feature (F) and target (T) affected both the learning and the expression of inhibitory stimulus control. Simple conditioned inhibition was established with both the serial and simultaneous procedures, but was revealed in performance only with simultaneous test trials. In contrast, negative occasion setting was established only with serial training compounds, but was revealed in both serial and simultaneous test compounds. Negative occasion setting was characterized by minimal transfer to separately trained target cues (but substantial transfer to a target of another feature-negative discrimination) and by its immunity to counterconditioning. Simple inhibition was characterized by its ready transfer to other target cues (regardless of training history) and by its elimination after counterconditioning. Both simple inhibitors and negative occasion setters readily suppressed the performance of new operant responses that were controlled by suitable target cues, but that transfer was not complete. Implications of these data for hypotheses about the loci of action of inhibitors and negative occasion setters in operant conditioning were discussed.