Primacy and recency effects in hierarchical renewal in rats

Previous studies on hierarchical resurgence produced mixed results regarding the order and magnitude of recurrence of responses trained initially (primacy effect) or more recently (recency effect). Although changes in contextual stimuli could explain such differences, in resurgence procedures contextual stimuli are not commonly presented, thus their effects on multiple operants trained sequentially remain unclear. Renewal procedures, in contrast, have been useful to determine the effects of exteroceptive contextual stimuli on response recurrence. Thus, primacy and recency effects were studied using a renewal procedure in which three contexts were presented sequentially. Lever presses by rats were reinforced on a different lever under each training context and were then exposed to extinction in a different context. Presses on a fourth lever were never reinforced. During renewal testing, the three training contexts were presented in the same or inverse order relative to training. A strong primacy effect was found in rats exposed to the original training order. Both primacy and recency effects were found when the rats were exposed to contexts in inverse order. These results suggest that the magnitude of renewal of hierarchically trained responses is affected by training order and order of presentation of contextual stimuli during testing.