The role of reward and reward uncertainty in episodic memory

•We test the role of reward-related factors in episodic memory.•Reward outcome is the strongest predictor of memory across four behavioural experiments.•No evidence that reward uncertainty improves memory in motivated learning.

Declarative memory has been found to be sensitive to reward-related changes in the environment. The reward signal can be broken down into information regarding the expected value of the reward, reward uncertainty and the prediction error. Research has established that high as opposed to low reward values enhance declarative memory. Research in neuroscience suggests that high uncertainty activates the reward system, which could lead to enhanced learning and memory. Here we present the results of four behavioural experiments that examined the role of reward uncertainty in memory, independently from any other theoretically motivated reward-related effects. Participants completed motivated word learning tasks in which we varied the level of reward uncertainty and magnitude. Rewards were dependent upon memory performance in a delayed recognition test. Overall the results suggest that reward uncertainty does not affect episodic memory. Instead, only reward outcome appears to play a major role in modulating episodic memory.