Fractionating the reward-memory literature: Instructed, item-related feedback, and item-unrelated feedback

Abstract

Over the last two decades, nearly one hundred studies have been published examining reward influences on memory. Implementations of reward-value procedures have varied markedly, as have other study characteristics, including images vs. words, intentional vs. incidental memory encoding, and recall vs. recognition tests. As such, the resulting state of the field has become unwieldy and somewhat difficult to identify consistent reward-memory effects from those that are inconsistent due to critical differences in the study methods. Here we provide an overview of these studies and fractionate their methods into three distinct procedures: instructed, item-related feedback, and item-unrelated feedback. Instructed studies tell participants of item-value associations during encoding with rewards earned during memory retrieval. In contrast, feedback studies ask participants to make responses during encoding, with rewards provided as feedback; memory retrieval itself is unrewarded. Some feedback studies require participants to make responses related to the to-be-remembered items, while others require participants to respond to an initial prompt before presenting an unrelated stimulus. While both procedures involve feedback, the first set of studies involves item-related feedback, and the second set has item-unrelated feedback. By fractionating the reward-memory literature into distinct procedures, an otherwise heterogenous mixture of study design characteristics becomes much more interpretable and the underlying cognitive mechanisms more clear. This additional clarity should improve predictions for future studies, as this framework helps identify which prior findings are more relevant, while also providing a summary of the current state of the field.