Ignoring the Unknown: Attentional Suppression of Unpredictable Visual Distraction

Recent findings have shown that people are capable of proactively inhibiting salient visual distractors in a scene when they know the color of the distractor, enhancing efficient search. Investigations of this suppression effect have concluded that it is not possible to suppress a distractor of an unknown color, implying a mechanism that operates only on a first-order, feature-specific level. However, with a modification to the search task, we show here for the first time that people can indeed suppress salient uniquely colored distractors even when not knowing their color in advance. The task requires participants to search for the most prevalent of several shapes in the display. In two experiments the presence of an unpredictable-color singleton facilitated search. An experiment with briefly presented probes confirmed proactive prevention of capture by the distractor. The results reveal a second-order or global-salience-based suppressive mechanism that facilitates visual processing. Public Significance Statement Natural visual scenes contain more information than can be processed at once, so the visual system must select portions of a scene for further processing. One way in which that selection occurs is by suppressing elements known to be irrelevant to one's current goals. Previous research has suggested that this suppression is possible only if specific features of the unwanted elements (e.g., their color) are known in advance; however, we show here, with a simple change to the experimental task, that people are indeed capable of suppressing distractors even without advance knowledge of their specific features. The results reveal a new mechanism that enhances efficient visual selection from the environment.