Proceedings of the Annual Meeting of the Cognitive Science Society

Surprising feedback alters memory of events. Reward prediction errors (RPEs) signal when feedback violates expectations. Although RPEs are known to influence memory, their role in pattern separation---a fundamental computation supporting discriminated episodic representations---remains unclear. We ask whether surprising outcomes strengthen memory encoding and if welcome (positive RPE) versus unwelcome (negative RPE) surprises differentially affect memory discrimination. We designed a variant of an established task developed to probe pattern separation, the Mnemonic Discrimination Task, that introduces post-trial reward and punishment feedback during encoding. We find that while surprising rewards enhance memory discrimination overall, trials with positive RPEs lead to better discrimination of similar lure items, but trials with negative RPEs lead to better recognition of repeated target items. Generalizing expectations to semantically similar stimuli further benefits discrimination. These findings suggest that surprising feedback enhances memory discrimination, with effects depending on the type of feedback and similarity structure of experiences.