Differential Neural Mechanisms Underlying Inhibition of Color and Dynamic Motion Distractors

Navigating visually complex environments requires focusing on relevant information while filtering out (salient) distractions. The signal suppression hypothesis posits that salient stimuli generate an automatic saliency signal that captures attention unless overridden by learned suppression mechanisms. In support of this, ERP studies have demonstrated that salient stimuli that do not capture attention elicit a distractor positivity (PD), a putative neural index of suppression. Yet, to date, this hypothesis has been primarily tested with color singletons, leaving it unclear if the PD reflects general suppression or is specific to color singletons. This study compared lateralized ERPs elicited by color singleton and dynamic motion distractors using a variant of the additional singleton paradigm that has been shown to result in proactive suppression of colored distractors. Behavioral results showed a singleton presence benefit for both distractor types, indicating distractor suppression. However, ERP data revealed clear differences in the underlying neural mechanisms: Color singletons elicited a PD component indicative of proactive suppression, whereas motion singletons elicited a later positivity preceded by an N2pc, suggesting reactive suppression. Our findings suggest that motion singletons, unlike color singletons, are suppressed reactively after initial capture. This study highlights the importance of considering distractor feature dimensions in understanding attentional suppression mechanisms and underscores the need for caution in establishing proactive suppression based on a single metric. Further research is needed to clarify the conditions under which the early PD reliably indicates proactive suppression and to explore the neural processes underlying the suppression of various salient distractors.