Repetition of critical search features underlies EEG lateralization, but not the Pd, in visual search

When searching for an item with specific visual features, salient nontargets (distractors) sometimes capture attention. The repetition of search features, such as target and distractor colors, affects both successful search and effective distractor handling. Nevertheless, the specific consequences of trial-to-trial feature repetition and search context on behavior and EEG components are poorly understood. Here, we investigated how search feature repetition shapes the electrophysiological and behavioral correlates of target processing and distractor handling, testing theoretically-informed predictions of these signals with a mixed-effects model comparison approach. In two experiments, the colors of a singleton distractor and fixed-shape target either repeated or changed unpredictably across trials. A color singleton target and distractor appeared in Experiment 1, allowing efficient search among pop-out items, while targets in Experiment 2 were not uniquely colored, forcing participants to rely on slower shape-feature search. Capture by the color singleton distractor occurred only in pop-out search (Experiment 1), but repetition reduced distractor interference. This pattern was paralleled by the contralateral N2pc-PD complex: following a search color switch, the target-related N2pc was greatly delayed, and salient distractors elicited an N2pc followed by a reactive PD. This biphasic response was absent in Experiment 2, where color was of limited usefulness to search. Early and late contralateral positivities were not sensitive to search relevance or feature repetition, suggesting that the PD is unrelated to preparatory suppression. Attention- and capture-related lateralization components are not universally elicited by target or distractor features, but are driven specifically by expected features important to the search task.