Visual search for changes in scenes creates long-term, incidental memory traces
Humans are very good at remembering large numbers of scenes over substantial periods of time. How good are they at remembering changes to scenes? In this study, we tested scene memory and change detection two weeks after initial scene learning. In Experiments 1-3, scenes were learned incidentally during visual search for change. In Experiment 4, observers explicitly memorized scenes. At Test, after two weeks, observers were asked to discriminate old from new scenes, to recall a change that they had detected in the study phase, or to detect a newly introduced change in the memorization experiment. Next, they performed a change detection task, usually looking for the same change from the study period. Scene recognition memory was found to be similar in all experiments, regardless of study task. In Experiment 1, more difficult change detection produced better scene memory. Experiments 2 and 3 supported a ‘depth of processing’ account for the effects of initial search and change detection on incidental memory for scenes. Of most interest, change detection during the Test phase was faster than during the Study phase, even when the observer had no explicit memory of having found that change previously. This result was replicated in two of three change detection experiments. We conclude that scenes can be encoded incidentally as well as explicitly and that changes in those scenes can leave measurable traces even if they are not explicitly recalled.