Repetition of critical search features modulates EEG lateralized potentials in visual search.

In visual search, the repetition of target and distractor colors enables both successful search and effective distractor handling. Nevertheless, the specific consequences of trial-to-trial feature repetition in different search contexts are poorly understood. Here, we investigated how feature repetition shapes the electrophysiological and behavioral correlates of target processing and distractor handling, testing theoretically informed predictions with single-trial mixed-effects modeling. In two experiments, the colors of a fixed-shape target and singleton distractor changed unpredictably across trials. Targets were color singletons in Experiment 1, allowing efficient search among pop-out items, but were not uniquely colored in Experiment 2, encouraging slower shape-feature search. Interference by the distractor occurred only in pop-out search but was reduced by repetition. This was paralleled by the contralateral electroencephalography (EEG) response: Following a search color change, the target-related N2pc was greatly reduced, and salient distractors elicited an N2pc followed by an enhanced PD. This biphasic response was absent in Experiment 2, where color was less useful to search. Overall, distractor positivities were not sensitive to feature repetition, suggesting that they are unrelated to preparatory suppression. Attention-related lateralization components are not universally elicited by target or distractor feature values but are driven specifically by expected features important to the search task.