Differential Multiple-Schedule Interactions in Rats

Three experiments examined multiple-schedule interactions in a free-operant paradigm for rats. In Exps. 1 and 2 three rats each and in Exp. 3 five rats were given extended multiple variable-interval baseline training before being shifted to multiple variable-interval extinction. Visual discriminative stimuli and regular extinction, which allowed nonreinforced responding, were used in Exps. 1 and 2, but auditory discriminative stimuli and retraction of the lever to prevent responding during extinction were used in Exp. 3. Positive behavioral contrast was observed in only one out of six rats in Exps. 1 and 2, while negative induction was observed in the other five subjects. However, contrast was observed at some point in training for all five subjects in Exp. 3. The differential multiple-schedule interactions were attributed to the introduction of an additional stimulus-reinforcer dependency with regard to the presence vs absence of the lever in Exp. 3. Results support an autoshaping or additivity account of behavioral contrast.

Counterconditioning of Conditioned Suppression in Rats

Rats were trained to suppress lever-pressing for food during a 1-min. tone CS followed by shock on 5 of 10 trials per session. Six counter-conditioning procedures were then carried our: (1) Regular Extinction; (2) Interference, in which extra food was delivered during the CS; (3) Toleration, in which a series of tones was employed starting at the lowest frequency and progressing to the original CS; (4) Toleration + Interference, a combination of the above procedures; (5) Flooding, in which a single 10-min. CS presenration was given each session; and (6) Flooding + Interference. Only Toleration + Interference significantly reduced the number of trials to a no-suppression criterion as compared with Regular Extinction. With respect to reducing the total amount of suppression during the counterconditioning period, Toleration + Interference was the most effective, followed in order by Toleration, Flooding, Interference, and Regular Extinction.

Effects of Nonresponse Acquisition on Latent Extinction in a Differential Reinforcement Setting

The present experiment was designed to determine the effects of 100%, 50%, and 0% reinforcement of nonresponse acquisition on the regular acquisition, latent extinction, and regular extinction of an instrumental running response. Ss were 78 male rats randomly assigned to six treatment conditions which included the administering of pretraining and training placements under varied reinforcement, followed by latent extinction and regular extinction test periods. Although the administration of pretraining and training placements had no significant effect on running speeds during acquisition, the results did indicate that Ss which had encountered nonreinforced placements prior to latent extinction were significantly more resistant to the effects of the pre-extinction placements. The discrimination hypothesis and frustration theory were considered as interpretations of the latent extinction data.