Searching Visual Displays: The Role of Attention

Abstract

Previous research suggests that (a) target localization tasks, (b) apprehension of spatial relations among stimuli, (c) critical features shared between target and non-target stimuli, and (d) mirror-image symmetry between target and non-targets each place demands on attention, resulting in poor search performance caused by capacity limitations. But, are these performance deficits actually caused by capacity limitations? Perhaps they are caused by early, pre-attentive visual processing or by noisy decision making instead of capacity limitations. If so, this has implications for the design of “user-friendly” displays to facilitate search performance. To address these questions, we controlled sensory effects and systematically varied the complexity and number of stimuli as well as whether non-targets were mirror-images of the target. Comparisons of data to theoretical predictions showed that capacity limitations occurred only when the target shared critical features with complex non-target stimuli, so that one must apprehend spatial relations of each object's component parts. No other factors resulted in capacity limitations. Moreover, although mirror-image symmetry adversely affected early visual preattentive processing, it did not place additional demands on attention.