Perceptual load does not modulate auditory distractor processing.

In vision, it is well established that the perceptual load of a relevant task determines the extent to which irrelevant distractors are processed. Much less research has addressed the effects of perceptual load within hearing. Here, we provide an extensive test using two different perceptual load manipulations, measuring distractor processing through response competition and awareness report. Across four experiments, we consistently failed to find support for the role of perceptual load in auditory selective attention. We therefore propose that the auditory system - although able to selectively focus processing on a relevant stream of sounds - is likely to have surplus capacity to process auditory information from other streams, regardless of the perceptual load in the attended stream. This accords well with the notion of the auditory modality acting as an 'early-warning' system as detection of changes in the auditory scene is crucial even when the perceptual demands of the relevant task are high.