Not so automatic: Task relevance and perceptual load modulate cross-modal semantic congruence effects on spatial orienting

Recent studies show that cross-modal semantic congruence plays a role in spatial attention orienting and visual search. However, the extent to which these cross-modal semantic relationships attract attention automatically is still unclear. At present the outcomes of different studies have been inconsistent. Variations in task-relevance of the cross-modal stimuli (from explicitly needed, to completely irrelevant) and the amount of perceptual load may account for the mixed results of previous experiments. In the present study, we addressed the effects of audio-visual semantic congruence on visuo-spatial attention across variations in task relevance and perceptual load. We used visual search amongst images of common objects paired with characteristic object sounds (e.g., guitar image and chord sound). We found that audio-visual semantic congruence speeded visual search times when the cross-modal objects are task relevant, or when they are irrelevant but presented under low perceptual load. Instead, when perceptual load is high, sounds fail to attract attention towards the congruent visual images. These results lead us to conclude that object-based crossmodal congruence does not attract attention automatically and requires some top-down processing.