The effects of visual perceptual load on detection performance and event-related potentials to auditory stimuli

Load Theory states that perceptual load prevents, or at least reduces, the processing of task-unrelated stimuli. This study systematically examined the detection and neural processing of auditory stimuli unrelated to a visual foreground task. The visual task was designed to create continuous perceptual load, alternated between low and high load, and contained performance feedback to motivate participants to focus on the visual task instead of the auditory stimuli presented in the background. The auditory stimuli varied in intensity, and participants signaled their subjective perception of these stimuli without receiving feedback. Depending on stimulus intensity, we observed load effects on detection performance and P3 amplitudes of the event-related potential (ERP). N1 amplitudes were unaffected by perceptual load, as tested by Bayesian statistics. Findings suggest that visual perceptual load affects the processing of auditory stimuli in a late time window, which is associated with a lower probability of reported awareness of these stimuli.