Multisensory Integration in Children and Adolescents with ASD: Susceptibility to the Flash-Beep Illusion

Background: Atypical sensory processing is a key characteristic of Autism Spectrum Disorder (ASD; APA, 2013). One specific sensory process, which allows individuals to experience the world as a coherent whole, involves the ability to efficiently integrate stimuli from multiple sensory modalities, or multisensory integration (MSI). Research suggests that altered MSI may partially underlie sensory-related behaviours in ASD (Iarocci & McDonald, 2006; Zhou et al., 2018). There has been mixed evidence as to whether the MSI of non-social information (e.g. information void of social content) is altered in individuals with ASD (e.g. Stevenson et al. 2014; Bao et al. 2017). Additionally, little is known about the development of MSI across age.

Objectives: The goal of the study is to investigate the MSI of non-social information in individuals with ASD at different periods of development using the flash-beep illusion task (Shams et al. 2002).

Methods: Thirty-one individuals with ASD (27 males, 4 females) and 57 typically developing (TD) individuals (32 males, 25 females), aged between 6 and 18 years, completed a sound induced flash illusion task. On every trial, participants were presented with either one (1F) or two flashes (2F) with either zero (0B), one (1B), or two beeps (2B) congruently in time, resulting in six different audiovisual conditions; 1F/0B, 1F/1B, 1F/2B, 2F/0B, 2F/1B, and 2F/2B. The fission illusion trial is the 1F/2B combination, and the fusion illusion trial is the 2F/1B combination. Participants were asked to indicate if they viewed ‘one’ or ‘two’ flashes on the screen. In parallel to the task, participants completed the Wechsler Abbreviated Scale of Intelligence 2^nd Edition (WASI-II) and the Sensory Profile Questionnaire.

Results: Participants were separated into four groups: ASD child (n=17; age <=12), ASD adolescent (n=14; age > 12), TD child (n=31; age <=12) and TD adolescent (n=26; age > 12). A 4 x 6 ANOVA (group x task condition) revealed a significant effect of condition (p<.001); a post-hoc Bonferroni comparison indicated that illusion trials were less accurate than non-illusion trials (suggesting participants were susceptible to the illusion). However, a significant group effect was also found (p<.001), with Bonferroni post-hoc analyses revealing a significant jump in accuracy between ASD children and ASD adolescents (p<.001), while there was no significant difference between TD children and TD adolescents (p=.547). This suggests a shift to being less susceptible to the illusion with age for ASD individuals but not TD individuals, specifically for the fusion illusion.

Conclusions: Our results revealed that TD individuals are susceptible to both illusions and this appears to be consistent across development. In comparison, adolescents with ASD were less susceptible to the fusion illusion than children with ASD, suggestive of less automatic MSI processes with age. Future research looking at MSI abilities, in ASD, for non-social information should do so within a developmental context.