Passive Suppression of Distractors in Visual Search

The ability to suppress distractors that appear repeatedly during visual search improves over time. For example, we previously asked participants to locate a gray square among three colored distractor squares (e.g., pink, orange, magenta) in a visual search task. After a “training” period, the three distractors sometimes changed to different sets of colors (e.g., blue, green, cyan). We found that the appearance of new (and very different) distractor colors slowed down search compared to “trained” distractors (Won & Geng, 2018). Although it was clear that experience with specific distractors improved suppression, it was unknown whether the enhanced suppression for “trained” colors was due to repeated active suppression of specific colors, or the passive viewing of those non-target colors during visual search (i.e., the habituation model; Turatto). Here, we address this question by adapting our previous paradigm to include a “habituation display” that was interleaved with visual search trials. The habituation display contained four colored circles and occurred briefly before each search display. Participants were instructed to ignore the circles but only focus on the search task. A control group experienced the same trial sequence, but was shown black circles during the “habituation display”. Consistent with the habituation model, search RT in the control group was slowed when new dissimilar distractors appeared, but no cost was found for the color-habituation group. This suggests that passive color exposure from the habituation displays led to equivalent suppression for new dissimilar distractors and trained distractors. We also tested the specificity of habitation by manipulating the color range of circles in the habitation display. We found that distractor suppression only occurred for new distractor colors that were seen on habituation displays. These findings indicate that distractor suppression may improve over time as a consequence of passive mechanisms of perceptual habituation and not “active” attentional mechanisms.