Intact lip-reading but weaker McGurk effect in individuals with high autistic traits.

A weaker McGurk effect is observed in individuals with autism spectrum disorder (ASD); weaker integration is considered to be the key to understanding how low-order atypical processing leads to their maladaptive social behaviors. However, the mechanism for this weaker McGurk effect has not been fully understood. Here, we investigated (1) whether the weaker McGurk effect in individuals with high autistic traits is caused by poor lip-reading ability and (2) whether the hearing environment modifies the weaker McGurk effect in individuals with high autistic traits. To confirm them, we conducted two analogue studies among university students, based on the dimensional model of ASD. Results showed that individuals with high autistic traits have intact lip-reading ability as well as abilities to listen and recognize audiovisual congruent speech (Experiment 1). Furthermore, a weaker McGurk effect in individuals with high autistic traits, which appear under the without-noise condition, would disappear under the high noise condition (Experiments 1 and 2). Our findings suggest that high background noise might shift weight on the visual cue, thereby increasing the strength of the McGurk effect among individuals with high autistic traits. © The British Society of Developmental Disabilities 2019.