Hierarchical resurgence.

In resurgence, conventionally a target response is trained and then extinguished while some alternative response is reinforced. In the most common procedure, when the latter is extinguished, the former resurges. The present experiments examined resurgence after two responses were trained sequentially and subsequently extinguished. In Experiments 1 and 2, keypecking to one key was trained and then extinguished as keypecking to a different key was trained then later extinguished. In both experiments, regardless of the spatial location of the different keys, the last-trained response resurged before the first-trained one. The results were replicated in Experiment 3 where reinforcement rate of the first-trained response was four times that of the second-trained response. The results in conjunction with earlier experiments suggest that resurgence occurs hierarchically, although whether more or less recently trained target responses resurge first or later may depend on both current and historical variables. The results also raise questions about the interpretation of responding on a control key that sometimes is included in resurgence experiments to isolate resurgence from extinction-induced responding.

Resurgence of time allocation.

The resurgence of time allocation with pigeons was studied in three experiments. In Phase 1 of each experiment, response-independent food occurred with different probabilities in the presence of two different keylights. Each peck on the key changed its color and the food probability in effect. In Phase 2, the food probabilities associated with each keylight were reversed and, in Phase 3, food was discontinued in the presence of either keylight. The food probabilities were .25 and .75, in Experiment 1, and 0.0 and 1.0 in Experiment 2. More time was allocated to the keylight correlated with more probable food in Phases 1 and 2, and in Phase 3 resurgence of time allocation occurred for two of three pigeons in Experiment 1, and for each of four pigeons in Experiment 2. Because time had to be allocated to either of the two alternatives in Experiments 1 and 2, however, it was difficult to characterize the time allocation patterns in Phase 3 as resurgence when changeover responding approached zero. In Experiment 3 this issue was addressed by providing a third alternative uncorrelated with food such that in each phase, after 30 s in the presence of either keylight correlated with food, the third alternative always was reinstated, requiring a response to access either of the two keylights correlated with food. In this experiment, the food probabilities were similar to those in Experiment 1. Resurgence of time allocation occurred for each of three pigeons under this procedure. The results of these experiments suggest that patterns of time allocation resurge similarly to discrete responses and to spatial and temporal patterns of responding.