Spatial correspondences of Audiovisual Stimuli on Double Flash Illusion Perception and its Cognitive Modeling

Perceptual processing integrates information from multiple sensory modalities to form a coherent representation of the environment. A classic example of such is the Sound-Induced Flash Illusion (SIFI), where the perceived number of visual flashes is altered by conflicting auditory stimuli. While the SIFI is a well-established phenomenon of multisensory integration, the influence of physical spatial characteristics--specifically stimulus eccentricity and spatial congruence--on integration levels remains debated.To address this gap, this study used the SIFI paradigm to investigate the effect of visual stimulus spatial location and the spatial congruence between auditory and visual stimuli on audiovisual integration. In Experiments 1 and 2, we found that when spatial attention was controlled via cueing, unimodal visual performance remained consistent across locations. However, the susceptibility to SIFI increased progressively from the central to the peripheral visual field, exhibiting a spatial pattern of Gaussian distribution. Bayesian modeling further supported this by showing that this spatial modulation was driven by an increase in the integration weight assigned audiovisual representations in the periphery, rather than changes in sensory uncertainty alone. Conversely, Experiment 3 demonstrated that the spatial congruence of audiovisual stimuli did not affect the SIFI or alter the integration processing. These findings refine our current understanding of the spatial modulation upon audiovisual integration. By incorporating the visual systems spatial properties into a Bayesian framework, we provide a computational explanation for the eccentricity-dependent nature of multisensory integration.