Attentional Capture by a Salient Distractor Enhances Target Search Efficiency through Object-based Attentional...

Salient distractors can automatically capture attention, but how object-based attention modulates this capture remains unclear. To address this issue, we conducted four experiments in a modified additional singleton paradigm where eight items were grouped into two perceptual objects based on the Gestalt principle of proximity. We manipulated whether the target and the singleton distractor belonged to the same or different objects. In Experiment 1, the target was the unique-shape item and the distractor was the unique-color item, which led to attentional capture. In Experiment 2, we reversed this assignment, with the target as the unique-color item and the singleton distractor as the unique-shape item, preventing attentional capture by the singleton distractor. The results revealed that the within-object benefit, manifested as shorter RTs when the target and singleton distractor belonged to the same object compared with different objects, was only present when the singleton distractor captured attention. Experiment 3 replicated the main findings of Experiment 1 with a simplified task. Experiment 4 provided electrophysiological evidence, whereby the within-object benefit was supported by the ERP results that the target elicited a larger N2pc and the singleton distractor elicited a larger PD for same- relative to different-object conditions. These findings align with the spreading account of object-based attention, whereby attentional capture by the singleton distractor spreads through the object to facilitate target processing when they are part of the same perceptual unit.