An experiment was conducted using a human instrumental learning task with the goal of evaluating the mechanisms underlying the deleterious effect of context-switching on responding to an unambiguous stimulus when contexts are informative to solve the task. Participants were trained in a context-based reversal discrimination in which two discriminative stimuli (X and Y) interchange their meaning across contexts A and B. In context A, discriminative stimulus Z consistently announced that the relationship between a specific instrumental response (R1) and a specific outcome (O1) was in effect. Performance in the presence of stimulus Z was equally deteriorated when the test was conducted outside the training context, regardless of whether the test context was familiar (context B) or new (context C). This result is consistent with the idea that participants code all the information presented in an informative context as context-specific with the context playing a role akin to an occasion setter.
