Irrelevant sights and sounds require spatial suppression: ERP evidence

Both real-world experience and behavioral laboratory research suggest that entirely irrelevant stimuli (distractors) can interfere with a primary task. However, it is as yet unknown whether such interference reflects competition for spatial attention - indeed, prominent theories of attention predict that this should not be the case. Whilst electrophysiological indices of spatial capture and spatial suppression have been well-investigated, experiments have primarily utilized distractors which share a degree of task-relevance with targets, and are limited to the visual domain. The present research measured behavioral and ERP responses to test the ability of salient yet entirely task-irrelevant visual and auditory distractors to compete for spatial attention during a visual task, while also testing for potentially enhanced competition from multisensory distractors. Participants completed a central letter search task, while ignoring lateralized visual (e.g., image of a dog), auditory (e.g., barking), or multisensory (e.g., image + barking) distractors. Results showed that visual and multisensory distractors elicited a P-D component indicative of active lateralized suppression. We also establish for the first time an auditory analog of the P-D component, the P-AD, elicited by auditory and multisensory distractors. Interestingly, there was no evidence to suggest enhanced ability of multisensory distractors to compete for attentional selection, despite previous proposals of a "special" saliency status for such items. Our findings hence suggest that irrelevant multisensory and unisensory distractors are similarly capable of eliciting a spatial "attend-to-me" signal - a precursor of spatial attentional capture - but at least in the present data set did not elicit full spatial attentional capture.