Abstract
An enduring question has been whether salient objects—such as color singletons—can automatically capture attention. As a potential resolution, the signal suppression hypothesis has proposed that salient distractors automatically attract attention via a bottom-up saliency signal, but these distractors can be suppressed via top-down control to prevent attentional capture. However, this account has been recently challenged on the grounds that the studies in support of it used color singletons that had low bottom-up salience. According to these stimulus-driven accounts, salient items can only be suppressed when they are weakly salient. At smaller set sizes (e.g., four-item displays), the singleton is contrasted with fewer nonsingleton distractors which may decrease the relative salience of the singleton. The current study directly tested this claim by using the additional singleton paradigm with high search-display set sizes, which should greatly increase the salience of the color singletons. In a series of experiments, we used ERP components to assess whether the salient singleton captured attention (the N2pc component) or if it was suppressed (the PD component). Both behavioral and electrophysiological evidence indicated that salient items were suppressed and did not capture attention. Furthermore, we independently verified the salience of our singletons using an established computational model of salience: the Image Signature Toolbox. Our saliency map analyses, which we describe in detail, suggested the color singletons were highly salient. Ultimately, the results support the signal suppression hypothesis and refute the claim that highly salient color singletons cannot be suppressed.