Autistic Communication and Imagination Sub-Traits Are Related to Audiovisual Temporal Integration in the Stream–Bounce Illusion

Autism spectrum disorder (ASD) is characterized by atypical social communication and restricted and repetitive behaviors; such traits are continuously distributed across nonclinical and clinical populations. Recently, relationships between ASD traits and low-level multisensory processing have been investigated, because atypical sensory reactivity has been regarded as a diagnostic criterion of ASD. Studies regarding an audiovisual illusion (the double-flash illusion) reported that social communication difficulties are related to temporal aspects of audiovisual integration. This study investigated whether similar relationships exist in another audiovisual illusion (the stream-bounce effect). In this illusion, two visual objects move toward each other, coincide, and pass each other, and the presentation of a transient sound at their coincidence induces a dominant perception that they bounce away from each other. Typically developing adults were recruited to perform experimental trials involving the stream-bounce effect. We measured their ASD traits using the Autism-Spectrum Quotient. The total quotient score was not related to any behavioral measurements of the effect. In contrast, for participants with higher difficulty in communication, the greatest magnitude of the stream-bounce effect occurred when the presentation timing of the sound tended to follow the visual coincidence. Participants with higher difficulty in imagination also showed the greatest magnitude of the effect when the presentation timing of the sound preceded that of the visual coincidence. Our findings regarding the stream-bounce effect, along with previous findings regarding the double-flash illusion, suggest that atypical temporal audiovisual integration is uniquely related to ASD sub-traits, especially in social communication.