Inflation of comparator stimuli following CS training

Abstract

Water-deprived rats served in seven conditioned lick suppression experiments designed to assess the effects on responding to a target CS of aseries of unsignaled USs given in the training context following completion of CS training. Such treatment has been hypothesized to increase (inflate) the associative strength ofthe background cues from training (putatively, the CS's comparator stimuli), thereby reducing responding to excitatory CSs and increasing the inhibitory potential of inhibitory CSs. Although posttraining extinction (deflation) ofthe CS's comparator stimuli usually decreases inhibitory potential and increases excitatory potential of the target CS, posttraining inflation of the comparator stimuli had no effect on either excitatory responding to the target CS or summation test performance indicative of conditioned inhibition. This outcome was consistently obtained across a number of training, inflation, and test conditions selected to maximize sensitivity to any possible effects of comparator inflation. Implications of these null results for the comparator hypothesis of conditioned response generation are discussed. expected when the US representation based on the CS is large, relative to that based on the comparator stimuli; inhibitory behavior is expected when the US representation based on the CS is small, relative to that based on the comparator stimuli. The comparator stimuli are some combination of the background cues that were present during training and any punctate cues that occurred proximal to the target CS during training. The exact weights of different comparator cues presumably are determined by the relative saliencies of the candidate cues.The comparator hypothesis makes many behavioral predictions that are identical to those generated by most contemporary theories of acquisition (e.g., Rescorla & Wagner, 1972). For instance, inflation of what we have termed comparator stimuli is well known to attenuate excitatory responding to a CS when the inflation occurs before or during CS training (US-preexposure effect and The comparator hypothesis (Miller & MatzeI, 1988; is a response rule that posits that conditioned responding is not only a positive function of the associative strength of the target conditioned stimulus (CS) at the time of testing, but is also a negative function of the associative strength at the time of testing of other stimuli (comparator stimuli) that were present during training (even when CS testing occurs outside the training context). The associative structure underlying the comparator hypothesis is illustrated in Figure 1. Presentation ofthe CS at the time oftesting is presumed to activate both a representation of the unconditioned stimulus (US) that is dependent on the CS-US linkage (Association 1) and a representation of the comparator stimuli that is dependent on the CS-comparator stimuli linkage (Association 2, which is necessary only when testing occurs in the absence of comparator stimuli). The active representation ofthe comparator stimuli, in turn, activates a ...

Recovery from the overexpectation effect: Contrasting performance-focused and acquisition-focused models of retrospective revaluation

“…Lattal and Nakajima extrapolate to conclude that, because CS X acquired biological significance in Phase 1, inflating the strength of Link 3 (Figure 1) by establishing a more strongly conditioned cue (A) as X's comparator stimulus in Phase 2 should not be able to attenuate responding to X. However, we draw attention to a fundamental difference between the inflation procedures that have failed to attenuate responding to an established conditioned excitor (e.g., Miller et al, 1990) and the procedure used to produce overexpectation.Consider backward blocking as a typical posttraining inflation procedure: After AX®US pairings in Phase 1, the blocking CS (A) is paired with the US in the absence of the target CS (X) during Phase 2. Despite this posttraining inflation of X's comparator stimulus, no attenuation in responding to X is ordinarily observed, perhaps because Link 2 (X-A) is being extinguished at the same time Link 3 (A-US) is being inflated.…”

“…Although the comparator hypothesis accounts well for both inflation and deflation (i.e., extinction) effects in theory, in practice only deflation effects have been achieved with a large degree of success. Inflation effects (e.g., backward blocking) have been much more elusive with animal subjects (e.g., Miller et al, 1990). Denniston et al (1996;see also Miller & Matute, 1996) have proposed a solution to this quandary.…”

“…(It is worthy of note that A®US pairings are procedurally a posttraining comparator inflation manipulation for Group OX.Same in this study [as well as in Experiment 3], which is predicted by the comparator hypothesis to attenuate responding to the CS. However, Miller, Hallam, andGrahame, 1990, have shown that inflation effects do not occur when biologically significant stimuli are -®US X Note-OX and Con refer to overexpectation and control treatments, respectively. Same and Diff indicate whether the A-US temporal interval during Phase 3 was the same as or different from, respectively, that of Phases 1 and 2.…”

Higher-order associative processing in Hermissenda suggests multiple sites of neuronal modulation.

“…For these later theories to account for the expression of blocking at the time of testing, it must be assumed that a third association is formed during conditioning trials, specifically, between the CS and the context in which it is trained, thus providing for context specificity (i.e., so that an excitatory context other than the CS training context does not block the expression of an association at the time of testing). The provision that an association is formed between all stimuli present on a conditioning trial and, specifically, between the CS and its training context is an integral feature of modern theoretical accounts of learning (e.g., Mackintosh 1985;Wagner and Brandon 1989;Miller et al 1991;Holland 1993;Capaldi and Neath 1995).…”

Biological significance attenuates overshadowing, relative validity, and degraded contingency effects

“…Along the same lines of research, Miller and Matute (1996; see also Denniston et al, 1996) were interested in the failure of previous research to demonstrate backward blocking (i.e., poor responding to X as a result of A-US trials that follow AX-US trials) with nonhuman subjects (see, e.g., Miller, Hallam, & Grahame, 1990;Schweitzer & Green, 1982). This failure contrasts with the successful demonstrations of backward blocking that have been obtained with humans in causaljudgment studies (see, e.g., BIOLOGICAL SIGNIFICANCE 173 Chapman, 1991;Shanks, 1985).…”