Dissociable contributions of reward and surprise to long-term memory

Reward and surprise recruit dopaminergic systems that support memory formation, yet their combined contribution to declarative long-term memory remains poorly understood. We leveraged music as a naturally rewarding and statistically structured stimulus to test how subjective reward and model-derived surprise interact during encoding to promote long-term memory. Seventy-five participants listened to and rated unfamiliar classical musical excerpts in an in-person behavioral paradigm. Reward was indexed by subjective pleasure ratings, and surprise was quantified using a validated computational model able to capture musical predictability. Memory was assessed after 24 hours using recognition and recollection measures. Reward and surprise each enhanced recognition memory, and both effects remained significant when modeled jointly despite their positive association. In contrast, recollection increased selectively for excerpts that were both more rewarding and more surprising. These findings show that subjective reward and model-derived surprise make functionally dissociable contributions to long-term memory for music: each supports recognition, whereas their combination most strongly enhances recollection. This interaction may help explain how new songs become rapidly memorable and “stick in our heads” even after a single exposure. More broadly, the results suggest that pleasurable and unexpected experiences are especially likely to be encoded as rich, durable memories.