Mutual gaze and later social attention development in infants at typical and elevated familial likelihood for ASD and/or ADHD

Atypical social attention is a feature of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), yet this has not yet been studied during toy-free naturalistic parent-infant interactions in infants at elevated likelihood of developing ADHD (EL-ADHD). We coded mutual gaze from caregiver-infant free-play videos recorded at 4-7 months in infants with typical likelihood (TL; n = 37), elevated likelihood of ASD (EL-ASD; n = 55), ADHD (EL-ADHD; n = 13) or both (EL-ASD + ADHD; n = 13). Face-orienting responses were measured using an eye tracking face pop-out task at 8-12 months, and ASD research diagnosis was established at 36 months. Results showed that EL groups engaged in more mutual gaze than TL peers, revealing a broad alteration in dyadic attention across neurodevelopmental likelihood. However, mutual-gaze duration did not differentiate infants who were later given an ASD diagnosis at age 3 years (n = 14). Furthermore, only in the EL-ASD group greater early mutual gaze predicted reduced subsequent orienting to faces. This association was mainly driven by those diagnosed with ASD at age 3, potentially indicating an ASD-specific developmental pathway. These findings highlight the value of naturalistic paradigms for probing early social attention and the need for larger, jointly analysed EL-ASD and EL-ADHD cohorts to refine neurodevelopmental models of typical and atypical infant social attention.