The allocation of attention in displays with simultaneously presented singletons

In an ERP experiment, we investigated whether a ‘permanent’ salient distractor changes the deployment of attention to target and nontarget singletons. Observers searched for a color target in a search array that mainly consisted of black vertical lines, but also always contained a line in a task-irrelevant color. Together with this distractor, a target or nontarget singleton was presented. Nontargets could be salient on the task-relevant dimension (color), or on a neutral dimension (line orientation). N2pc amplitude was maximal for targets, no N2pc was elicited by color nontargets, and orientation nontargets elicited an inverse N2pc. Targets and color nontargets elicited larger N2 amplitude than orientation singletons. P3 amplitude was high for relevant and low for irrelevant singletons. Targets also elicited higher reaction times and more errors. Attention seemed thus driven by the target feature, and by its feature dimension, even when constant distraction on that dimension had to be suppressed.

► ERP measures of visual selective attention.
► Color targets, color and orientation nontargets shown with permanent color distractors.
► N2pc maximal for targets, absent for color nontargets, inverted for orientation nontargets.
► Attention guided by dimensional task relevance, despite constant distraction.