Degraded contingency revisited: Posttraining extinction of a cover stimulus attenuates a target cue's behavioral control.

Abstract

In a Pavlovian conditioning situation, unsignaled outcome presentations interspersed among cueoutcome pairings attenuate conditioned responding to the cue (i.e., the degraded contingency effect). However, if a nontarget cue signals these added outcomes, responding to the target cue is partially restored (i.e., the cover stimulus effect). In 2 conditioned suppression experiments using rats, the effect of posttraining extinction of the cover stimulus was examined. Experiment 1 found that this treatment yielded reduced responding to the target cue. Experiment 2 replicated this finding, while demonstrating that this basic effect was not due to acquired equivalence between the target cue and the cover stimulus. These results are consistent with the extended comparator hypothesis interpretation of the degraded contingency and cover stimulus effects. KeywordsPavlovian conditioning; degraded contingency; cover stimulus; contingency; comparator hypothesisThe degraded contingency effect, originally reported by Rescorla (1966Rescorla ( ,1968, is observed when unsignaled presentations of an unconditioned stimulus (US) are administered during training sessions in which a conditioned stimulus (CS) and a US are paired. These added US presentations diminish responding to the CS, independent of baseline responding in the context. The critical finding of these experiments was that responding to the CS was reduced by a manipulation that did not reduce the contiguity between the CS and the US. Early accounts of classical conditioning assumed that contiguity between stimuli was both necessary and sufficient for classical conditioning to occur (e.g., Bush & Mosteller, 1955). Therefore, the degraded contingency effect seemed inconsistent with pure contiguity accounts of classical conditioning that required only that the CS be consistently closely followed by the US.Initial explanations of the degraded contingency effect posited that attention to, or learning about, the CS was attenuated by contextual stimuli that became excitatory during the unsignaled presentations of the US, thereby preventing subjects from learning the association between the CS and the US (e.g., Mackintosh, 1975;Rescorla & Wagner, 1972). These sorts of accounts are similar to those offered for blocking (Kamin, 1968), but with the training context acting as the blocking cue. For example, the Rescorla-Wagner model of learning explains blocking by assuming there is a finite amount of associative strength supportable by a given US, and the majority of this associative strength is absorbed by the blocking CS during the elemental training phase (A-US), leaving little for the blocked CS at the time of subsequent compound training (XA-US). Applied to the degraded contingency preparation, US-alone presentations make the training context highly excitatory so it comes to block acquisition of the CS-US association. Essentially, this account of the degraded contingency effect assumes that the Correspondence concerning this article should be addressed to Ralph R. Miller...

Evaluation of ambiguous associations in the amygdala by learning the structure of the environment

“…5b XII, Supplementary Fig. 9a), and qualitatively similar predictions to previous studies 28 using related experimental paradigms (Supplementary Fig. 9a).…”

Protection from extinction provided by a conditioned inhibitor

“…That is, stimuli that are not directly associated with the target CS can still influence responding to it. This is consistent with a number of other demonstrations in which a target’s behavioral control is affected by second-order comparators (e.g., McConnell et al, 2009; Urushihara, Wheeler, Pineño, & Miller, 2005; Witnauer & Miller, 2007). For example, McConnell et al demonstrated protection from latent inhibition and attenuation of this protection effect after extinction of a second-order comparator stimulus.…”

Interactions between retroactive-interference and context-mediated treatments that impair Pavlovian conditioned responding

“…Thus, the comparator hypothesis predicts an effect of degraded contingency treatment in Experiment 1 based on a strong association between O and the training context. 1 This account of degraded contingency has been supported by similar studies from our laboratory that indicate that subjects can recover from the effect of degraded contingency if the training context is extinguished after targetstimulus training (e.g., Urcelay & Miller, 2006;Witnauer & Miller, 2006). Thus, degraded contingency appears to be dependent on associative status of the context at test.…”