Reward enhances false memory in a long term

Remembering valuable information is important in one's daily life. Although reward has been shown to enhance true memory through value-directed remembering, its effect on false memory, especially in the long term, is not well understood. We combined the pictorial DRM paradigm with a reward-learning task to investigate the effect of reward on false memory and its persistence over time. In Experiment 1, certain lists of pictures were rewarded, while others were not, then participants' memories were tested immediately, 1 d later, or 1 week later. In Experiment 2, lists were associated with either a high or low reward. Results from two experiments consistently showed that reward not only enhanced false recognition for lure pictures but also significantly increased false binding between lure pictures and reward, forming false rewarding memories. Importantly, this reward-enhanced false memory effect persisted even after one week, whereas true memories of reward decreased over time. Our results suggest a critical role of time in shaping both false and true episodic memories of reward experiences.