Sub-clinical levels of autistic traits impair multisensory integration of audiovisual speech

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder characterized by restricted interests, repetitive behavior, deficits in social communication and atypical multisensory perception. ASD symptoms are found to varying degrees in the general population. While impairments in multisensory speech processing are widely reported in clinical ASD populations, the impact of sub-clinical levels of autistic traits on multisensory speech perception is still unclear. The present study examined audiovisual (AV) speech processing in a large non-clinical adult population in relation to autistic traits measured by the Autism Quotient. AV speech processing was assessed using the McGurk illusion, a simultaneity judgment task and a spoken word recognition task in background noise. We found that difficulty with Imagination was associated with lower susceptibility to the McGurk illusion. Furthermore, difficulty with Attention-switching was associated with a wider temporal binding window and reduced gain from lip-read speech. These results demonstrate that sub-clinical ASD symptomatology is related to reduced AV speech processing performance, and are consistent with the notion of a spectrum of ASD traits that extends into the general population.