Attentional Effects in Visual Search: Relating Search Accuracy and Search Time

Abstract In this article, I will describe a program of research that distinguishes among the leading theories of divided attention. Divided attention has often been studied using set-size effects in visual search. A typical search task is illustrated in Figure 1. In both panels the task is to search for the target disk which has a higher luminance than the distractor disks. The subject is to respond “yes” when the higher luminance disk is present and “no” when it is absent. The target is present in both of the panels of Figure 1. The panels differ in the number of disks present: the panel on the left has a set size of 2, and the panel on the right has a larger set size. Increasing set size usually decreases performance. These set size effects have been measured both in accuracy paradigms that use brief displays to prevent multiple eye fixations and in response time paradigms that allow extended inspection of the display with multiple eye fixations. Such set-size effects are of interest because different theories of attention predict set-size effects of different magnitudes.