Investigating the effect of selective attention and the spatial relationships of competing auditory stimuli on the sound-induced flash illusion

The sound-induced flash illusion (SIFI) provides a way of testing multisensory integration through perceptual illusion. Studies disagree on the influence of auditory-visual spatial (in)congruence on SIFI. To better assess the possible influence of spatial proximity, we manipulated the spatial congruence of competing auditory stimuli. Study participants were presented with two timbrally distinct concurrent auditory stimuli of one or two beeps and a visual stimulus composed of one or two flashes. One auditory stimulus always matched the number of visual flashes, and the other did not. The auditory-matching stimulus was manipulated to either be spatially congruent or not with the visual flashes, which could occur centrally or to the left or right. Participants were instructed to report the number of flashes they saw. For half of each session participant’s attention was not directed and had no knowledge of flash location on the coming trial, while in the other half there was a visual spatial cue prior to the ...