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