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,…

Operant and classical conditioning are major processes shaping behavioral responses in all animals. Although the understanding of the mechanisms of classical conditioning has expanded significantly, the understanding of the mechanisms of operant conditioning is more limited. Recent developments in "Aplysia" are helping to narrow the gap in the…