It Took Me by Surprise: Examining the Retroactive Enhancement Effect for Memory of Naturally Unfolding Events

In two experiments, we examined how accurately participants remembered details from a naturalistic, first-person perspective film, which ended with the protagonist either encountering or not encountering an unexpected detail. Participants who watched the film with the unexpected detail at the end displayed superior accuracy for preceding event details compared to those who watched a film without such a detail. This retroactive enhancement effect generalized across both visual and auditory details, but it appeared contingent upon the unexpected detail being relevant to the event's story. The effect occurred whether participants' memory was tested immediately or after a two-day delay. The present findings can be seen as consistent with prior work on synaptic tagging and long-term potentiation, but the phenomenon of retroactive enhancement has not been demonstrated previously for naturally unfolding events. Implications of the findings are discussed in relation to eyewitness memory and intrusive memories in post-traumatic stress disorder. General Audience Summary In our daily lives, we sometimes encounter unexpected situations, such as looking up while driving and seeing a car swerve into our lane. In this study, we examined how experiencing such a surprising moment during an event may affect people's memory for what happened up until that point in time. Specifically, we had participants watch films depicting a naturally unfolding event from a first-person perspective and asked them to imagine themselves as the films' protagonists. Some of the films included something unexpected happening at the end, while all other aspects of the films were the same up until that point in time. We found that when people experienced something unexpected (such as running into a person as they were leaving a house), they were more accurate when their memory was tested for details that had occurred during the event prior to that unexpected moment. We also found this effect was present only if people encountered something unexpected that was related to the narrative or story of the event. These findings support the idea that experiencing something surprising during events in our daily lives may have a retroactive effect upon our memory for what came before, including improving our memory for details we may not have otherwise remembered. As such, there are potential implications for these results in terms of understanding how intrusive memories of traumatic or stressful events may