RESEARCH ARTICLE A Salient and Task-Irrelevant Collinear Structure Hurts Visual Search

Salient distractors draw our attention spontaneously, even when we intentionally want to ig-nore them. When this occurs, the real targets close to or overlapping with the distractors benefit from attention capture and thus are detected and discriminated more quickly. How-ever, a puzzling opposite effect was observed in a search display with a column of vertical collinear bars presented as a task-irrelevant distractor [6]. In this case, it was harder to dis-criminate the targets overlapping with the salient distractor. Here we examined whether this effect originated from factors known to modulate attentional capture: (a) low probability— the probability occurrence of target location at the collinear column was much less (14%) than the rest of the display (86%), and observers might strategically direct their attention away from the collinear distractor; (b) attentional control setting—the distractor and target task interfered with each other because they shared the same continuity set in attentional task; and/or (c) lack of time to establish the optional strategy. We tested these hypotheses by (a) increasing to 60 % the trials in which targets overlapped with the same collinear dis-tractor columns, (b) replacing the target task to be connectivity-irrelevant (i.e., luminance discrimination), and (c) having our observers practice the same search task for 10 days. Our results speak against all these hypotheses and lead us to conclude that a collinear dis-tractor impairs search at a level that is unaffected by probabilistic information, attentional setting, and learning