Relations Between Preferential Looking to Synchronous Audiovisual Speech and Expressive Language in Infants With Autistic and Non-Autistic Siblings.

Differences in audiovisual processing may influence language development in autism. We characterized preferential looking to temporally synchronous audiovisual speech in fifty infants (28 elevated-likelihood [54% male]; 22 population-level-likelihood [50% male]) aged 12-18 months. We first tested whether preferential looking to synchronous audiovisual speech differed between groups; population-level-likelihood infants demonstrated greater preferential looking to synchronous audiovisual speech relative to elevated-likelihood infants by 18 months. We then assessed whether preferential looking to synchronous audiovisual speech was related to concurrent expressive language (1) directly, (2) via vocalization complexity, and (3) as moderated by age, sex, and familial likelihood group. Infants completed an eye tracking task and standardized communication and language assessments at 12-18 months. The population-level-likelihood infants demonstrated greater preferential looking to synchronous audiovisual speech relative to elevated-likelihood infants by 18 months. Preferential looking to synchronous audiovisual speech was not directly and unconditionally associated with concurrent expressive language. However, moderation and mediation analyses showed that preferential looking to synchronous audiovisual speech was significantly associated with concurrent expressive language through increased vocalization complexity in male infants. Implications for research, theory, and clinical practice are discussed.