In for a pound, in for a penny: How the opportunity to gain reward influences the competition for memory resources

When people encounter items that they believe will help them gain reward, they later remember them better than others. A recent model of emotional memory, the emotional Context Maintenance and Retrieval model (eCMR), predicts that these effects would be stronger when stimuli that predict high and low reward can compete with each other both during encoding and retrieval. We tested this prediction in two experiments. Participants were promised {pound}1 for remembering some pictures, but only a few pence for remembering others. Their recall of the content of the pictures they saw was tested after one minute and in Experiment 2, also after 24 hours. Memory at immediate test showed effects of list composition. Recall of stimuli that predicted high reward was greater than of stimuli that predicted lower reward, but only when high- and low-reward items were studied and recalled together, not when they were studied and recalled separately. More high-reward items in mixed lists were forgotten over a 24-hour retention interval compared to items studied in other conditions, but reward did not modulate the forgetting rate, a null effect which should be replicated in a larger sample. These results confirm eCMRs predictions, although further research is required to compare that model against alternatives.