Interaction between preexposure and overshadowing: Further analysis of the extended comparator hypothesis

Abstract

Three experiments with rats used conditioned suppression of barpress to test predictions of the extended comparator hypothesis, which assumes that the effectiveness of (first-order) comparator stimuli in modulating responding to a target conditioned stimulus (CS) is itself modulated by other (second-order) comparator stimuli. Experiment 1 demonstrated that both pretraining exposure to the target CS alone (i.e., CS-preexposure effect, also known as latent inhibition) and pretraining exposure to a compound of the target CS and nontarget CS (i.e., compound-CS-preexposure effect) counteract overshadowing, and that posttraining deflation (i.e., extinction) of the overshadowing stimulus attenuates responding to the target CS when overshadowing is preceded by a CS-preexposure treatment (i.e., yields a CS-preexposure effect), but not when overshadowing is preceded by a compound-CS-preexposure treatment. Experiment 2 examined the consequences of posttraining associative inflation of the overshadowing stimulus or the preexposure companion stimulus following conjoint compound-CS-preexposure and overshadowing treatment. Experiment 3 examined the consequences of posttraining inflation of the overshadowing stimulus or the context following conjoint CS-alone preexposure and overshadowing treatment. The results support the expression-focused comparator view in contrast to recent acquisition-focused models of retrospective reevaluation.

Counteraction between overshadowing and degraded contingency treatments: Support for the extended comparator hypothesis.

“…As implemented, the training context also acts as the target cue's first-order comparator stimulus, and the overshadowing cue serves as the target cue's second-order comparator stimulus. Simulation of Experiment 1 after Savastano, Arcediano, Stout, and Miller's (2003) implementation of the extended comparator hypothesis. All parameters were the same as those used by Savastano, Arcediano, and colleagues, and the numbers of trials were the same as those used in Experiment 1 of the present series of studies.…”

“…This prediction is illustrated in Figure 2, which depicts simulations of simple acquisition, overshadowing, the degraded contingency effect, and the interaction of overshadowing and degraded contingency. We used Savastano, Arcediano, et al's (2003; see also Stout & Miller, 2005) mathematical implementation of the extended comparator hypothesis, including exactly their parameters and the number of trials used in the present Experiment 1. As shown in Figure 2, the simulation indicates that when both treatments are presented together, a partial recovery from overshadowing and from degraded contingency is predicted.…”

Experimental challenges to theories of classical conditioning: Application of an attentional model of storage and retrieval.

“…Therefore, preexposure should result in less overshadowing. Savastano, Arcediano, Stout, and Miller (2003) showed how a mathematical version of the extended comparator hypothesis can explain experimental results showing that preexposure and overshadowing cancel each other. In their simulations, responding in the PRE ϩ OVER group is 20% and 6% stronger than in the OVER and the PRE ϩ CON groups, respectively, whereas in our simulations, these ratios are 47% and 65%.…”

Connectionism and Classical Conditioning

“…While formalization of the comparator hypothesis has not yet been completed (e.g. Savastano et al, 2003), it is important to determine whether the absence of inhibition in it restricts the kinds of problems that it can solve, as it would in a perceptron.…”