People often fail to detect a change between two visual scenes and retrieval failure has been suggested as a reason. We investigated the possibility that retrieval blocking underlies this failure by examining the error pattern in recognizing the pre-change object. The results of Experiment 1 showed that participants were biased toward selecting the lure that was similar to the post-change object when they failed to recognize the pre-change object. This bias was also observed in Experiment 2 when there was sufficient time to encode and consolidate the pre-change object and the bias was as strong as correct recognition in Experiment 3 when participants divided attention during encoding and comparison. The bias in memory error remained significant even when participants had the option to select an "I don't remember" response in Experiment 4. In Experiment 5, the bias was observed after participants successfully detected a change at an invalidly cued location and after they failed to detect a change at a validly cued location. These findings suggest that blocking can lead to retrieval failure in change detection when participants are aware of a change yet unable to retrieve verbatim traces and also when participants are unaware of a change and use the post-change object to retrieve the identity of the previous object at the same location.
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