Abstract
Folk, Remington, and Johnston (1992) proposed that attentional capture by task-irrelevant stimuli occurs only when they share with the target its defining feature; namely it is impossible for a non-contingent stimulus to capture attention. Nevertheless, in Folk's series of studies supporting this hypothesis, only 4 items were used in the target display. We test the generality of this hypothesis by using larger set sizes and different SOAs since previous results suggest that increasing set size enhances stimulus salience and stimulus-driven activation is highest around the time the stimulus appears. The target was defined by either a color or a flash, and a distractor preceded the target that either had the same color, or also was a single flash. The target feature or location was never contingent on the distractor, and participants were instructed to ignore the distractor. Our results show that a stimulus that is not contingent on attentional control settings can also capture attention, especially in displays with large set size, and this capture effect occurs early and decreases with SOA. However, only non-contingent flash distractors capture attention, and color distractors do not. In conclusion, purely stimulus-driven attentional capture by a flash does occur and the asymmetrical results in the capture effect by flash and color distractors suggest that flash and color play different roles in capturing attention.
Supported by the National Science Council of Taiwan, NSC95-2752-H-002-007-PAE and 95-2413-H-002-020