AbstractThis study investigated if visual attention can influence multisensory integration at the onset of a reaching action. On each trial, one of three squares was identified as the target, and participants executed a pointing movement to that square. At movement onset, secondary stimuli consisting of two flashes (F) and one or two beeps (B) that included unimodal (2F), congruent (2F2B), and incongruent (2F1B) conditions were presented within the target of the reaching movement (i.e., attended), in the adjacent square (i.e., unattended close), or two squares away from the target (i.e., unattended far). After each trial, participants reported the perceived number of flashes. Although increased visual eccentricity could increase the weight on audition and susceptibility to the fusion illusion in the incongruent condition, visual attention was expected to influence sensory integration and thus increase susceptibility to the fusion illusion. As expected, accuracy in both the unimodal and congruent conditions was significantly better in the attended condition relative to the unattended close and far conditions. In the incongruent condition, however, susceptibility to the fusion illusion was greater in the attended and unattended far conditions as compared to the unattended close condition. Such findings may suggest that the auditory-induced visual illusion captured attention exogenously, thus yielding stronger fusion percepts in the attended vs. the unattended close condition. The greater susceptibility to the fusion illusion in the unattended far and attended conditions could thus be due to visual eccentricity and attention, respectively. Nevertheless, visual attention can influence multisensory integration processes.
Acknowledgments: Natural Sciences and Engineering Research Council of Canada (NSERC); Canada Foundation for Innovation (CFI); Ontario Research Fund (ORF); JSPS KAKENHI (JP17H00753); Japan Science and Technology Agency CREST (JPMJCR14E4)