The conceptual relatedness of post-encoding interference influences forgetting for central details in complex memories.

The importance of the post-encoding period for memory retention is clear from studies of retroactive interference. However, it is less clear how the nature of post-encoding information determines the mnemonic fate of complex memories, which contain both central details describing the unfolding of the event and peripheral details which provide perceptual richness. The goal of the present study was to test whether interfering narratives composed of central details varying in conceptual similarity causes retroactive interference for details from the encoded memory. Experiment 1 used a between-subjects design where participants encoded videos depicting complex events (e.g., going to a restaurant) followed by a post-encoding period consisting of an unfilled delay or an interfering narrative that was either related (e.g., going to a restaurant) or unrelated to the event (e.g., taking an art class). The interfering narratives were composed of only central details and were presented auditorily, to minimize overlap with peripheral details in the videos. Half of the videos were recalled immediately, and half were recalled after 24-hours. We found that central details were forgotten more in the unrelated post-encoding group than the other two groups. Experiment 2 replicated the difference in central detail recall between related and unrelated post-encoding interference using a within-subjects design. We reveal that retroactive interference for complex memories may be determined both by the conceptual similarity of the interfering information and by the overlap between the types of details being interfered with.