In three experiments with rats, we demonstrated that a conditioned response that is learned and extinguished in one context (Context A) can be renewed when the conditioned stimulus (CS) is tested in a second context (Context B). In Experiments 1 and 3, the effect was observed in conditioned suppression; in Experiment 2, it was produced in appetitive conditioning. The result occurs when Contexts A and B are equally familiar, equally associated with reinforcement, or equally associated with both reinforcement and nonreinforcement. The results extend the range of conditions known to produce the renewal effect, and they are consistent with the view that retrieval of extinction depends more on the context than does retrieval of conditioning.

In four experiments utilizing an appetitive conditioning preparation, reacquisition of conditioned responding was found to occur both rapidly and slowly following extinction. In Experiment 1, acquisition of responding to a tone that had been conditioned and extinguished occurred more rapidly than acquisition in either a group that received equivalent exposure to the food unconditioned stimulus or a "rest" control group that received only exposure to the apparatus in the first two phases. However, reacquisition was impaired relative to acquisition in a "learning-experienced" group that had previously received conditioning and extinction with a different stimulus. Experiments 2 and 3 produced similar results, but also found that high responding during reacquisition was confined to trials that followed reinforced, rather than nonreinforced, trials. Experiment 4, in which very few initial conditioning trials were used, produced reacquisition that was slow compared with both learning-experienced and rest controls. The results are consistent with a role for sequential learning: Reacquisition is rapid when animals have learned that reinforced trials signal other reinforced trials.

Conditioned suppression was used with rats to study the effects of extending conditioned stimuli (CSs) before versus after the delivery of unconditioned stimuli. These extensions are termed B and A extensions, respectively. Within-group designs were used to compare the effects of extending CSs when 2-min parts of those CSs were separated by temporal gaps of 6 min versus a separation of no gap. The results were as follows: (a) B extensions weakened conditioning more than did A extensions, with or without gaps; (b) under some conditions, this asymmetrical effect persisted with extended training; (c) gaps between 2-min parts of a B extension had no detectable effect; and (d) under some parameter values, gaps between 2-min parts of an A extension weakened conditioning significantly. These results are better predicted by the Sometimes Opponent-Process model (SOP;

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