Abstract
Attention capture is not only measured in terms of reaction time (RT) benefits to find a certain target, but also in terms of RT costs produced by certain distractors. Thus, one would expect that if the number of such distractors is systematically increased, RT costs would be even higher. The present study looked at cumulative interference effects from multiple dynamic events on target detection. In Experiment 1 the search display consisted of a combination of static, abrupt-onset (onset) and moving items which could all be target or distractors with an equal probability. In line with previous studies, participants were faster when the target was an onset than when it was a static item and slowest when it was a moving item. Surprisingly, the type of distractor(s) did not have any effect on search performance nor did it depend on the type of target. In Experiment 2, motion was replaced by an onset of motion (motion-onset). Based on previous studies (Abrams and Christ, 2003), which have shown that motion-onset captures attention, we expected that the competition between onset and motion-onset items would lead to a distractor-type effect. Again, motion-onset targets did not capture attention, and there was no effect of distractor type. In Experiment 3, the display size was increased from three to eight items and the number of onsets was systematically varied between zero and eight. Results showed the typical advantage for onset targets in comparison to static targets. Furthermore, RTs to an onset target increased as a (power) function of number of onsets, while RTs to a static target were unaffected by the number of onsets. Thus, the cost of having multiple onset distractors did occur with eight-item, but not with three-item displays, suggesting that a limited capacity bottleneck might be involved in the attentional prioritization process.