The relationship between cognitive ability and susceptibility on the Sound-Induced Flash Illusion (SIFI) across development

Introduction. Multisensory integration (MSI) is the ability to combine multiple sources of sensory information into one coherent whole. While understanding the developmental trajectory of MSI is important, it is imperative to account for other variables which may contribute to this ability, such as cognitive functioning (or IQ). MSI performance has been most frequently compared to other attributes (i.e., language), with IQ being scarcely considered as an associated attribute. The aim of this study was to examine the age at which MSI for non-social information matures and the role of IQ. Methods. 101 neurotypical participants were placed into child (6-9ys, Mage=7.6), school-age (10-13ys, Mage =11.8), adolescent (14-17ys, Mage=15.0) and adult (18+ys, Mage=22.3) age groups. All participants completed the Sound-Induced Flash Illusion (SIFI), where they were asked to indicate how many flashes were perceived while ignoring auditory cues. Performance on the fusion (2F1B) and fission (1F2B) conditions were examined. Participants also completed a cognitive assessment (Wechsler Abbreviated Scale of Intelligence-2; WASI-2), with a primary interest on perceptual reasoning (PRI) and verbal comprehension (VCI) indices. Results. A 2 (illusion conditions) x 4 (groups) ANOVA revealed a significant main effect of condition (p<.01) and interaction effect (p<.01), with post-hoc analyses demonstrating increased overall susceptibility for the fission condition; however, adults were significantly less susceptible on this condition compared to the other age groups. Hierarchical multiple regressions revealed that higher PRI scores were associated with increased susceptibility to the fission condition across age groups. Conclusion. Results suggest decreasing susceptibility solely to the fission illusion with increasing age, and that PRI may be related to susceptibility to this illusion. These results highlight the need to consider non-verbal IQ in assessing performance on non-social MSI tasks across development. Future studies should continue to explore the relationship between IQ and MSI, including social MSI and verbal IQ.