Jonga Kwon¹ (), Suk Won Han¹, Seonbeom Heo¹, Sohyun Kim¹; ¹Chungnam National University

Stimuli that perceptually stand out from their surroundings often capture attention involuntarily, potentially disrupting goal-directed visual search. The present study examined the processing locus of this interference caused by a salient singleton distractor, focusing on whether the disruption occurs at an early perceptual stage or during post-perceptual processes such as decision-making and response selection. To dissociate these stages, we measured both accuracy and reaction time (RT): perceptual interference should impair both measures, whereas non-perceptual interference should selectively affect RT. Participants performed two types of visual search tasks—a line-orientation search thought to rely on parallel processing, and a rotated T/L search that requires serial attentional shifts. On half of the trials, a salient color singleton distractor was presented. In the initial experiments, singleton distractors increased RT only in the line-orientation task under longer display durations (p < .05), with no accuracy costs in either task (ps > .37), suggesting primarily non-perceptual interference. However, because these RT effects were obtained under perceptually demanding conditions, they are also consistent with the possibility that singleton distractors delay the accrual of sensory information rather than leaving perception untouched. To directly test this, we conducted additional experiments in which a local mask was presented at the target location immediately after the search display, interrupting ongoing sensory encoding. Under these masked conditions, singleton distractors significantly reduced both accuracy (ps < .001) and RT (ps < .01). Across experiments, the presence of a singleton distractor impaired accuracy only when sensory encoding was truncated by masking, indicating that attentional capture delays the build-up of perceptual information. These findings suggest that distractor-driven interference originates at the perceptual stage, but becomes observable in accuracy only when the encoding interval is limited.

Acknowledgements: This research was supported by the Chungnam National University research grant and the National Research Foundation grant (NRF) funded by the Korea government (No. NRF-2024S1A5A2A01019821)