Reward enhancement of item-location associative memory spreads to similar items within a category.

The experience of a reward appears to enhance memory for recent prior events, adaptively making that information more available to guide future decision-making. Here, we tested whether reward enhances memory for associative item-location information and also whether the effect of reward spreads to other categorically-related but unrewarded items. Participants earned either points (Experiment 1) or money (Experiment 2) through a time-estimation reward task, during which stimuli-location pairings around a 2D-ring were shown followed by either high-value or low-value rewards. All stimuli were then tested for location memory or recognition (yes/no), immediately and after a 24-hour delay. Across both experiments (combined analysis), there was a robust improvement in location memory following high-value rewards, even though evidence supporting this effect was reliable in Experiment 2 but not in Experiment 1. The memory-enhancing effect of reward was observed on both the immediate and delayed location-memory tests. Reward-enhanced memory for both directly rewarded stimuli and categorically related stimuli that were not directly rewarded. No reliable effect of reward value on yes/no recognition-memory performance was observed in either experiment. We hypothesise that reward enhances the consolidation of recent experience and conceptually related memories to make these more available for future decisions.