The Modified Law of Effect Explains the Partial Reinforcement Extinction Effect

Thorndike’s Law of Effect provides a framework for understanding the selection of behaviors given specific environmental reward contingencies. Though a highly influential model, especially given its resurgence in popularity to understand habitual behaviors, it fails to predict several well-documented behavioral phenomena and incorrectly views extinction as the unlearning of a previously acquired association. Blaisdell, Stolyarova, & Stahlman (2016) proposed modifications to Thorndike’s original law that address these issues and greatly increases the model’s explanatory power. This modified Law of Effect (MLOE) also provides a testable account of the Partial Reinforcement Extinction Effect (PREE). The PREE is the paradoxical finding of more rapid extinction to a continuously reinforced cue than to a partially reinforced cue, and has challenged many theoretical accounts of learning. Simulations of the MLOE confirm these predictions. Two experimental paradigms, one using pigeons and the other using humans, show support for the Modified Law of Effect’s explanation of the PREE.