Irrelevant sights and sounds require spatial suppression: ERP evidence

Both real-world experience and behavioural 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 utilised distractors which share a degree of task-relevance with targets, and are limited to the visual domain. The present research measured behavioural 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 PD component indicative of active lateralized suppression. We also establish for the first time an auditory analogue of the PD component, the PAD, 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 dataset did not elicit full spatial attentional capture.