Incidental change detection and working memory load in a dual-task paradigm

Many years of research have been devoted to examining the limits of our visual system. Not only are there limits on the amount of information we can attend to, but there also are limits in the number of items we retain from one moment to the next. Previous data from our lab suggests the capacity limits of short-term memory are relevant for incidental change detection tasks. For example, observers who searched for a complex visual cue during a change video detected fewer changes than observers who searched for a simple visual cue. In addition, observers performed poorly when they had to complete a verbal processing task in conjunction with incidental change detection. The current set of experiments further examined working memory load and change detection in a dual task paradigm, in which change detection was not the primary task. Observers were instructed to search for a more difficult concurrent visual cue. While the cue was much more complex than ones used in prior studies, the task only required observers to store that particular cue while watching the change video. In general, a working memory load effect was demonstrated only when the concurrent task involved the storage and manipulation of information. For example, any task that required observers to hold and process the given cue resulted in change blindness. However, if observers only had to store the given cue, they showed successful change detection. This suggests that the processing/manipulation component of working memory is particularly important for incidental change detection, while storage alone may have little effect on incidental change detection ability.