Witnessing postevents does not change memory traces,but can affect their retrieval

The results of three experiments suggest that a memory trace for an event is not altered by witnessing similar events, but that postevents can interfere with its retrieval. On an immediate recall test, details from an original story (e.g. wrench) were recalled less often if a subsequent story mentioned a ‘screwdriver’ than if it did not. The interference effect occurred if people were asked to recall details fromboth stories (tool —— ——), but not if people were asked to recall primarily from the first story. Thus, the interference effect in immediate recall was averted if the target trace could be activated selectively (Experiments 1a and 1b). A more general interference effect was found after a day. Fewer targets from the original story were recalled if the second story was presented just before the test than if both stories occurred a day earlier. Thus, the second story interfered with recall only if it emphasized contextual retrieval cues that did not match the trace for the targets (Experiment 2). Copyright © 2001 John Wiley & Sons, Ltd.