Top-down control of attention under varying task loads.

The performance of a goal-directed task is often interrupted by task-irrelevant distractors. This distractor interference has well been demonstrated in a large body of studies employing the Eriksen flanker paradigm. A notable finding regarding this issue is that distractor interference is attenuated by increased perceptual load or the presence of non-target stimuli diluting distractors. Besides increased perceptual load or the presence of diluters, we hypothesized that either suppression of distractor or enhancement of target via top-down attentional control would also contribute to modulating distractor interference. To test this, we had participants identify a target stimulus while ignoring a distractor under three different conditions; under low load, only the target and distractor was presented, while under high load, the target was surrounded by non-target letters. In the dilution condition, the target was accompanied by non-targets, whose colors were distinct from the target. Importantly, following the task stimuli, a probe stimulus was presented either in the target location, non-target location, or distractor location. As results, under low load, attention was captured by the target stimulus in a bottom-up manner at the early stage of processing. By contrast, in the high load and dilution conditions, attention was focused on the target in a top-down manner. Taken together, we suggest that increasing perceptual load or presenting diluters incentivizes the establishment of top-down bias toward the target stimulus, which plays a role in attenuating distractor interference.