Redundancy gains in audio–visual search

Abstract

This study concerns stimuli-driven perceptual processes involved in target search among concurrent distractors with a focus on comparing auditory, visual, and audio–visual search tasks. Previous works, concerning unimodal search tasks, highlighted different preattentive features that can enhance target saliency, making it ‘pop-out’, e.g., a visually sharp target among blurred distractors. A cue from another modality can also help direct attention towards the target. Our study investigates a new kind of search task, where stimuli consist of audio–visual objects presented using both audio and visual modalities simultaneously. Redundancy effects are evaluated, first from the combination of audio and visual modalities, second from the combination of each unimodal cue in such a bimodal search task. A perceptual experiment was performed where the task was to identify an audio–visual object from a set of six competing stimuli. We employed static visual blur and developed an auditory blur analogue to cue the search. Results show that both visual and auditory blurs render distractors less prominent and automatically attracts attention toward a sharp target. The combination of both unimodal blurs, i.e., audio–visual blur, also proved to be an efficient cue to facilitate bimodal search task. Results also showed that search tasks were performed faster in redundant bimodal conditions than in unimodal ones. That gain was due to redundant target effect only without any redundancy gain due to the cue combination, as solely cueing the visual component was sufficient, with no improvement found by the addition of the redundant audio cue in bimodal search tasks.