Visual short-term memory load and detecting feature changes

Observers may demonstrate change blindness while having nonetheless represented the changing details. In our previous experiments, we found that observers who did not detect changes to actors in brief videos were sometimes able to recognize the actors in a lineup just as accurately as observers who did see the change. In the current experiment, we explore the hypothesis that this pattern of results can be observed when attention is directed at the changing actors while keeping visual short-term memory relatively free of the need to represent visual detail. Observers searched for simple (low VSTM load) or complex (high VSTM load) visual targets in a video depicting a conversation between two actors. Observers were also told that the cues may or may not appear on the body of one of the actors. Consistent with previous experiments, the task of searching for the cue increased change detection compared to situations where the task does not focus the subjects on the changing features. In addition, observers who searched for the complex cue detected significantly fewer changes than observers who searcher for the simple cue (45% vs. 64%). On the recognition test, observers in the complex cue condition were more accurate when they saw the change while observers in the simple cue condition were equally accurate whether they saw the change or not. This pattern of results suggests that the need to retain the visual details of a complex cue in VSTM can preempt representations of extra, noncompared, visual details that would otherwise allow successful recognition in the face of change blindness.