Sensitivity to temporal synchrony and selective attention in audiovisual speech in infants at elevated likelihood for autism: A preliminary longitudinal study.

Autism Spectrum Disorder is a highly heritable condition characterized by sociocommunicative difficulties, frequently entailing language atypicalities that extend to infants with a familial history of autism. The developmental mechanisms underlying these difficulties remain unknown. Detecting temporal synchrony between the lip movements and the auditory speech of a talking face and selectively attending to the mouth support typical early language acquisition. This preliminary eye-tracking study investigated whether these two fundamental mechanisms atypically function in infant siblings. We longitudinally tracked the trajectories of infants at elevated and low-likelihood for autism in these two abilities at 4, 8, and 12 months (n = 29). We presented two talking faces (synchronous and asynchronous) while recording infants' gaze to the talker's eyes and mouth. We found that infants detected temporal asynchronies in talking faces at 12 months regardless of group. However, compared to their typically developing peers, infants with an elevated likelihood of autism showed reduced attention to the mouth at the end of the first year and no variations in their interest to this area across time. Our findings provide preliminary evidence on a potentially atypical trajectory of reduced mouth-looking in audiovisual speech during the first year in infant siblings, with potential cascading consequences for language development, thus contributing to domain-general accounts of emerging autism.