Mechanisms of resurgence II: Response-contingent reinforcers can reinstate a second extinguished behavior.

Three experiments with rat subjects examined resurgence of an extinguished instrumental response using the procedure introduced by Epstein (1983) with pigeons. There were three phases: (1) initial acquisition of pressing on a lever (L1) for pellet reward, (2) extinction of L1, and (3) a test session in which a second lever (L2) was inserted, briefly reinforced, and then extinguished. Experiment 1 confirmed that if pressing L2 delivered 20 pellets followed by extinction, rats would resume L1 responding in the final test. Experiment 2 compared the effects of response-contingent and non-contingent rewards delivered upon insertion of L2. Although insertion of L2 alone did not increase L1 responding, response-contingent and non-contingent rewards led to comparable increases in L1 responding. Experiment 3 found that the delivery of non-contingent pellets during extinction of L1, which would be expected to reduce the ability of pellets to set the occasion for the L1 response, also reduced the effects of both response-contingent and non-contingent rewards during the final test. The results indicate that in this method, the resurgence treatment leads to an increase in L1 pressing due to simple presentation of the pellet; delivering the reinforcer after extinction of L1 reinstates L1 responding by setting the occasion for the L1 response.