Two mechanisms of distractor dilution: visual selection in a continuous flow.

Distractor dilution, which reflects little distractor interference in a context of high display load but easy target processing, has sparked debate between theoretical viewpoints. These two viewpoints can be integrated into a model in which grouping and the efficacy of attention control influence the relative activation strength between the distractor and nontarget representations. In a context in which nontargets and a distractor were presented in separate task-irrelevant regions, the dilution effect was replicated when nontargets were grouped with the target, and the effect was reduced when the distractor was grouped with the target (Experiments 1 to 3). When nontargets were presented in a task-relevant region and the distractor was presented in a task-irrelevant region, the dilution effect was replicated when attention control was effective in accumulating nontarget information (Experiment 4b). The dilution effect was reduced when control was ineffective in a short stimulus duration of 50 ms (Experiment 4a), in a circular arrangement of stimuli (Experiment 5), or in a context in which the distractor location was random (Experiment 6). The dilution effect occurred either before (Experiment 1b) or after (Experiment 4b) the engagement of attention control on a continuum of visual selection through bottom-up and top-down process interactions.