Protecting the Rescorla-Wagner (1972) theory: A reply to Spicer et al. (2020).

Rescorla (2001) used the compound test procedure to compare associative changes to cues located at different points on a performance scale. He found that associative changes to cues conditioned in compound are not necessarily equal, as predicted by common error term theories like Rescorla and Wagner (1972), but instead are larger for the poorer predictor of a trial outcome. Hence, Rescorla proposed a modification to the Rescorla-Wagner model whereby associative change is calculated as the product of 2 error terms: a common error term, as in the original model, and a unique error term for each cue present, which accounts for his findings that the poorer predictor of a trial outcome undergoes more associative change. In a recent study, Spicer, Mitchell, Wills, and Jones (2020) reported findings that appear to be inconsistent with Rescorla's proposal. These authors compared associative changes to cues that differed in associative strength as well as the certainty with which they predicted a trial outcome: One cue had greater strength than did the other, but its prediction of the trial outcome was less certain. Spicer et al. found that the cue that evoked a larger prediction error (the more certain cue) underwent less (not more) associative change and, thereby, concluded that associative change in people is not primarily determined by prediction error. Instead, they argued that cues that predict certain outcomes are somewhat protected from further associative change (theory protection), resulting in greater change to cues that predict uncertain outcomes. In this article, we offer an alternative explanation for the Spicer et al. findings using an approach described by Holmes, Chan, and Westbrook (2019). We show that if the learning-to-performance mapping function is a double sigmoid across the full range of associative strength, the Rescorla-Wagner model accommodates Rescorla's compound test results, as well as those reported by Spicer et al. (PsycInfo Database Record (c) 2021 APA, all rights reserved).