Effects of the amount of acquisition and contextual generalization on the renewal of instrumental behavior after extinction

Travis P. Todd Neil E. Winterbauer Mark E. Bouton 0 ) Department of Psychology, University of Vermont , 2 Colchester Avenue, Burlington, VT 05405-0134, USA Four experiments with rat subjects examined the role of context during the extinction of instrumental (freeoperant) behavior. In all experiments, leverpressing was first reinforced on a variable-interval 30-s schedule and then extinguished before being tested in the extinction and renewal contexts. The results identified three important variables affecting the renewal effect after instrumental extinction. First, ABA and ABC forms of renewal were strengthened by increasing the amount of acquisition training. This suggests that the strength of the association learned during acquisition, or the final level of performance, influences the degree of renewal after extinction. The effect of the amount of training was modulated by the second factor, the degrees of generalization from the acquisition and extinction contexts to the test context. The third variable was acquisition training in multiple contexts, which was shown to strengthen ABC renewal. Methodological, theoretical, and practical implications are discussed. Instrumental behavior is acquired when the performance of a response, such as a leverpress, results in the delivery of a biologically significant outcome, such as a food pellet. In such a procedure, the rate of leverpressing usually increases as training progresses. One way in which the behavior can be reduced is through a procedure known as extinction. Here, the outcome (the food pellet) is no longer presented when the - response is made, and the rate of behavior (i.e., leverpressing) decreases. Extinction is an important phenomenon because it is a fundamental process of behavior change. Furthermore, instrumental learning processes have been suggested to play a role in drug addiction (e.g., Everitt & Robbins, 2005) and overeating (e.g., Bouton, 2011), and extinction is one procedure that can reduce unwanted instrumental behaviors. One important fact about extinction is that it does not result in the erasure of the original learning. Extensive research in Pavlovian conditioning (see Bouton, 2002, 2004) has indicated that instead extinction likely reflects new learning that is especially context dependent. This context dependence is demonstrated in the renewal effect. In renewal, following extinction in one context, responding returns (renews) when testing occurs outside the context of extinction. Although there is a growing parallel between Pavlovian extinction and instrumental extinction, the extent of the parallel regarding the renewal effect has not been clear. Several reports, with drugs or food as reinforcers, have demonstrated a renewal of extinguished instrumental responding when subjects are removed from the extinction context and returned to the original acquisition context (Bossert, Liu, Lu, & Shaham, 2004; Chaudri, Sahuque, & Janak, 2009; Crombag & Shaham, 2002; Hamlin, Clemens, & McNally, 2008; Hamlin, Newby, & McNally, 2007; Nakajima, Tanaka, Urushihara, & Imada, 2000; Zironi, Burattini, Aircardi, & Janak, 2006). However, there is less evidence that removal from the extinction context alone (without a return to the acquisition context) results in response recovery. For example, several authors have failed to detect AAB renewal, in which acquisition and extinction occur in Context A and testing occurs in Context B (see Bossert et al., 2004; Crombag & Shaham, 2002; Nakajima et al., 2000). If instrumental extinction is similar to Pavlovian extinction, removal from the extinction context should then be sufficient to cause renewal of responding. A recent series of experiment by Bouton, Todd, Vurbic, and Winterbauer (2011) demonstrated three forms of renewal following instrumental extinction. In one experiment, renewal of instrumental responding occurred when extinction took place in Context B and testing occurred in Context A (ABA renewal). Responding also renewed when extinction occurred in Context A and testing occurred in Context B (AAB renewal). In a different experiment, renewal occurred when rats were trained, extinguished and tested in three separate contexts (ABC renewal). Overall, these experiments demonstrated a parallel between Pavlovian and instrumental extinction: Both seem to reflect new learning that is especially context dependent. One question about the data reported by Bouton et al. (2011) was the size of the ABC renewal effect. Although statistically robust (e.g., 15 of 16 rats responded more in Context C than in Context B during testing), the increase in the rate of leverpressing from the context of extinction to the test context was not especially large numerically, and clearly was not as large as in ABA renewal. However, it is worth noting that the Bouton et al. (2011) experiments involved a very modest amount of acquisition training (only five or six 30-min sessions). The aim of the present experiments was thus to further compare ABA and ABC renewal and to examine variables that might influence their magnitudes. The purpose of Experiment 1 was to ask whether ABC renewal could be strengthened by giving extended acquisition training prior to extinction. Experiment 2 compared the effects of the amount of acquisition on both ABC and ABA renewal. Experiment 3 tested the hypothesis that context similarity may influence instrumental renewal by encouraging retrieval of acquisition or extinction during testing. Finally, Experiment 4 tested the hypothesis that acquisition in multiple contexts increases ABC renewal. Overall, the results suggest that the amount of acquisition training, contextual similarity, and acquisition in multiple contexts strongly influence the strength of renewal after the extinction of instrumental learning. Experiment 1 examined whether ABC renewal would be strengthened by a training procedure that increased the final level of acquisition performance. In our previous demonstration of ABC renewal (Bouton et al., 2011), the rat subjects received only 5 30-min sessions of acquisition. In the present experiment, one group of rats received 12 daily 30-min sessions of leverpress training in Context A, and another group received 4 daily sessions. Following 4 sessions of extinction in Context B, all rats were tested for renewal. The renewal test was performed within subjects: All rats were tested in both Contexts B and C in a counterbalanced order (Bouton & Ricker, 1994; Bouton et al., 2011; Rescorla, 2008). If the amount of training affects ABC renewal, then the group given more acquisition would be expected to press more in Context C than would the group given the relatively brief acquisition period. Subjects The subjects were 16 naive female Wistar rats purchased from Charles River Laboratories (St. Constance, Quebec). They were between 75 and 90 days old at the start of the experiment and were individually housed in suspended wire mesh cages in a room maintain (...truncated)