CROSS-DIMENSIONAL PERCEPTUAL SELECTIVITY

Three visual search experiments tested whether top-down selectivity toward particular stimulus dimensions is possible during preattentive parallel search. Subjects viewed multielement displays in which two salient items, each unique in a different dimension-that is, color and intensity (Experiment 1) or color and form (Experiment 2 and 3)-were simultaneously present. One of the dimensions defined the target; the other dimension served as distractor. The results indicate that when search is performed in parallel, top-down selectivity is not possible. These findings suggest that preattentive parallel search is strongly automatic, because it satisfies both the load-insensitivity and the unintentionality criteria of automaticity.