It is well accepted that multisensory integration has a facilitative effect on perceptual and motor processes, evolutionarily enhancing the chance of survival of many species, including humans. Yet, there is limited understanding of the relationship between multisensory processes, environmental noise, and children's cognitive abilities. Thus, this study investigated the relationship between multisensory integration, auditory background noise, and the general intellectual abilities of school-age children (N = 88, mean age = 9 years, 7 months) using a simple audiovisual detection paradigm. We provide evidence that children with enhanced multisensory integration in quiet and noisy conditions are likely to score above average on the Full-Scale IQ of the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV). Conversely, approximately 45% of tested children, with relatively low verbal and nonverbal intellectual abilities, showed reduced multisensory integration in either quiet or noise. Interestingly, approximately 20% of children showed improved multisensory integration abilities in the presence of auditory background noise. The findings of the present study suggest that stable and consistent multisensory integration in quiet and noisy environments is associated with the development of optimal general intellectual abilities. Further theoretical implications are discussed.

Multisensory processing and attention 2Research highlights:• Multisensory processes in children are significantly related to attention abilities.• The McGurk Effect, where vision alters auditory perception, is more pronounced in children with better visual-spatial and audiovisual dual attention abilities.• The Stream-Bounce Effect, where sound alters visual perception, is more pronounced in children with better auditory sustained attention.• In school-age children, the relationship between attention type and multisensory processing is flexible and task-dependent.Multisensory processing and attention 3

In adults, it is well known that multisensory processes can be modulated by attention, however, little is understood about the development of this interplay. This study investigated the relationship between multisensory integration and attention in children. The Tests of Everyday Attention for Children (TEA-Ch) was used to assess visual attention (Sky Search subscale), sustained auditory attention (Score DT subscale) and audio–visual attention (Sky Search DT subscale, i.e., Sky Search and Score DT combined) in 59 children (age range: 7–12 years). The Wechsler Intelligence Scale for Children — Fourth Edition — Australian (WISC-IV) was used to measure general intellectual abilities. Multisensory integration was gauged using the stream-bounce illusion (SBI). Participants were presented with two discs moving horizontally toward each other either with no sound or with a click sound at −400 ms, −250 ms, 0 ms, +250 ms, +400 ms relative to the time of collision of the two discs. The perception of the SBI significantly increased when the sound was presented at or near the time of collision. Correlation analyses showed that both age (, ) and measures of auditory sustained attention (Score SD, , ) significantly predicted the SBI. Furthermore, children with high Score DT measures (age standardised scores > 11, ) reported significantly more SBIs, even when the effects of age and IQ were controlled for, when compared with children in the low score range (age standardised scores < 9, ). These findings suggest that multisensory integration in children is partly dependent on the stability of sustained auditory attention.