Spontaneous Recovery of Responding following Forward and Backward Blocking

1. Spontaneous Recovery of Responding following Forward and Backward Blocking Oskar Pineño, Kouji Urushihara and Ralph R. Miller State University of New York at Binghamton

2. Introduction • Recovery of responding following forward blocking has been mainly studied using the following manipulations: • Reminder treatments (e.g., US-alone presentations prior to testing): • Balaz, Gutsin, Cacheiro, and Miller (1982). • Schachtman, Gee, Kasprow, and Miller (1983). • Extinction of the blocking stimulus following blocking treatment: • Arcediano, Escobar, and Matute (2001). • Blaisdell, Gunther, and Miller (1999). • Spontaneous recovery of responding following stimulus competition has been studied in paradigms such as: • Overshadowing: Kraemer, Lariviere, and Spear (1988). • Relative validity: Cole, Gunther, and Miller (1997).

3. However, the study of spontaneous recovery from blocking has received little attention. • It has been demonstrated by: • J. S. Miller, Jagielo, and Spear (1993). • Batsell (1997). • But these experiments were performed on the US preexposure effect (i.e., forward blocking by the context) using a conditioned taste aversion preparation.

4. Therefore it remained unclear whether: • Spontaneous recovery can be observed when punctuate, instead of contextual, cues serve as the blocking stimulus. • Spontaneous recovery from blocking could be observed in a preparation different from the conditioned taste aversion paradigm. • In fact, some studies on blocking between punctuate stimuli showed enhancement, rather than attenuation, of forward blocking following a retention interval (J. S. Miller, McKinzie, Kraebel, & Spear, 1996).

5. Moreover, no study has assessed spontaneous recovery from backward blocking. • The study of spontaneous recovery of responding following forward and backward blocking is of theoretical importance. • Different models of associative learning differ in their predictions regarding the effect of presenting a retention interval after forward and backward blocking.

7. The present experiments were performed in a conditioned lick suppression preparation with rats. • The experimental treatments were performed within a sensory preconditioning paradigm in order to maximize the observation of backward blocking (Denniston, Miller, & Matute, 1997; Miller & Matute, 1996).

8. Experiment 1- Purpose and design • Experiment 1 assessed whether the interpolation of a long retention interval before testing could recover responding to a forward and/or backward blocked CS.

9. Experiment 1 - Results

10. Experiment 2 - Purpose • Experiment 2 aimed to replicate the findings of Experiment 1 with three main differences: • Blocking was studied in a 3-phase design. • This allowed elimination of differences in the amount of time elapsing from training to testing of the X-Outcome association between conditions forward and backward blocking. • The control condition was given B-Outcome, instead of B-, trials. • B-Outcome trials better control for the potential influence of exposure to the Outcome (e.g., latent inhibition to the Outcome).

11. Experiment 2 - Design

12. Experiment 2 – Results

13. Experiment 3 - Purpose • Experiment 3 tested two alternative explanations of the results of Experiments 1 and 2. • In these experiments, recovery of responding after blocking treatment could be due to: • A flattening of the generalization gradients of CSs X and A during the time interval. In this case: • CSs X and A would become more similar during the retention interval. • As a consequence, the animals could have responded to CS X as if this CS was CS A. • An increase of fear over the retention interval (i.e., incubation of fear).

14. Experiment 3 contrasted different explanations of Experiments 1 and 2 by using a slight variation of the design of Experiment 2. • As in Experiment 2, in Experiment 3: • In Experiment 3, CSs X and A were trained in compound, followed by Outcome. • CS A was trained either before or after the AX-O trials. • However, contrary to Experiment 2, in Experiment 3: • CS A (instead of Outcome) was paired with the US. • The presentations of Outcome were irrelevant, and were included only to minimize any difference between Experiments 2 and 3.

15. In Experiment 3, if responding to X decreased following the retention interval, then: • The results of Experiments 1 and 2 are not explicable in terms of a flattening of the generalization gradients or incubation of fear. • Both views predict that a retention interval should enhance responding to X (i.e., assuming that responding to X was not maximal before the retention interval).

16. Experiment 3 - Design

17. Experiment 3 – Results

18. Discussion • Experiments 1 and 2 demonstrated, for the first time, spontaneous recovery from both forward and backward blocking. • Experiment 3 showed that responding to X was attenuated in both condition APre and condition APost following a retention interval. • Applied to Experiments 1 and 2, the results of Experiment 3 suggest that the observed increase in responding to the blocked CS after a retention interval was not due to a flattening of generalization decrements or incubation of fear.

19. Presentation Direct US Link 1 of target CS representation (X) Link 2 Comparison CR Comparator stimulus Indirect US Link 3 representation representation (A) • Among the different models of learning that account for forward blocking and/or backward blocking, only the comparator hypothesis (Miller & Matzel, 1988) could be extended to explain spontaneous recovery from blocking.

20. If the comparator hypothesis assumed that all associations wane equally with time, a retention interval should more strongly impair the indirect activation of the outcome, than the direct activation of the outcome. • Regardless of the appropriateness of this account, the present experiments can be taken as the first demonstrations of spontaneous recovery from both forward and backward blocking.