Bimodal discrimination tasks involving different hierarchical processing levels reveal a late stage interaction between multisensory integration and attention

摘要

Multisensory integration and attention have been studied independently and a vastamount of literature exists for both phenomena. Researchers have recently raisedquestions, however, as to how these two processes interact. For example, doesmultisensory integration occur automatically without the need for attention; or doesintegrative processing require attention for it to occur? If the latter, do attention andintegration act in parallel throughout all information processing levels, or does oneoperation need to exist to advance the other? The present study sought to answer thesequestions through a series of within-subject tasks spanning multiple layers of theprocessing hierarchy. Forty-five participants completed three tasks involving audiovisual,integrated stimuli in which they discriminated the location of a visual target stimulusfrom nontarget distractors while being simultaneously presented with congruent auditorytones. The first task involved the discrimination of shapes and was shown to be preattentivein nature, with no facilitatory effect being observed in response tosimultaneously presented visual and auditory stimuli. The second task involved thediscrimination of die-point stimuli, which required high attentional demand. A trendtowards intersensory facilitation was observed in this task, but was not significant. Thethird and final task involved the discrimination of integrated shapes and die-points, whichalso required a high attentional load. Findings from this conjunction search revealed asurprising reversal of intersensory facilitation. These results suggest that attention has alimited capacity in terms of multisensory processing, and that specific intersensoryfacilitation requires a unique amount of attentional involvement. Results are discussed interms of feature integration theory, the perceptual load hypothesis, and attentional inhibition. This study also highlights the need for multisensory research to pay closeattention to the influence of methodology, task sensitivity, and cognitive hierarchy wheninterpreting results.