Adaptive Learning and Forgetting in an Unconventional Experimental Routine

Learning and forgetting were assessed concurrently in two experiments that involved the same unconventional routine. The schedule of reinforcement changed every session. Sessions were run back-to-back with a 23-hour mid-session break such that in a single visit to the testing chamber, the subject completed the second half of one session and the first half of the next. The beginning of a new session was either signaled or unsignaled. Experiment 1 involved concurrent variable interval-variable interval schedules with four possible reinforcer ratios. Response allocation was sensitive to the richer schedule and was retained through the mid-session break. Experiment 2 involved peak-interval schedules of varying durations. Temporal discrimination was rapidly acquired before and after the mid-session break, but not retained. Signaling the session change decreased control by past contingencies in both experiments, demonstrating that learning and forgetting can be investigated separately. Forgetting is often thought of as the inability to remember, but remembering and forgetting allow behavior to adapt to a changing environment in distinct and separable ways. These results suggest that the temporal structure of information can impact animals’ capacity to forget and remember.