Relationship between Selection Accuracy and Exposure in Visual Search

The physical similarity between the target and the irrelevant items, and the number of irrelevant items, were varied to obtain curves relating accuracy of target location to exposure, and reaction time to exposure. Two groups of subjects searched circular displays where similarity differed for each group, and number and exposure varied within groups. The results indicated that the relationships between accuracy and exposure were the more informative since they directly reflected processing, particularly when the exposure was very brief. These time versus accuracy curves were negatively accelerated, showing rapid increases in accuracy for approximately 50 ms with very slow (if any) increases for longer exposures. As it was not possible to account for these accuracy variations in terms of simple serial or parallel models of information processing, they were seen as reflecting processing by preattention and focal attention. Further analysis suggested that the times required for preattentive processing were brief and have a probability distribution.