Global and fine-grained social perception across age in typical development and in autism spectrum disorder: an eye-tracking study

Autism spectrum disorder (ASD) is characterized by marked difficulties in social interaction, with atypical eye-gaze behavior as a core feature. Eye-tracking studies have consistently reported reduced attention to social information in ASD across a large range of paradigms, suggesting that social perception abnormalities span multiple levels of processing, from initial orienting toward socially salient stimuli to fine-grained allocation of attention to social cues. Most studies have relied on group-level comparisons, and how these levels relate at the individual level remains unclear, particularly regarding inter-individual variability and whether these processes rely on shared mechanisms across development. We collected eye-tracking data from 150 participants with ASD and typical development (TD), from 2.6 to 26.7 years old, using two paradigms: (i) a preferential looking task contrasting human motion versus geometric motion to assess social orienting, and (ii) a naturalistic paradigm with complex social scenes to measure attention to socially informative regions (eyes). Inter-individual variability was characterized using Shapiro–Wilk and Levene’s tests. Group differences and associations between paradigms were analyzed using general linear models controlling for age and sex. Individuals with ASD looked significantly less to human motion ( p = 1.4 × 10⁻⁵) and to the eyes of characters ( p = 4.6 × 10⁻⁴) compared to TD participants, across the full age range. Both groups exhibited substantial inter-individual variability in gaze behavior, with continuous and normally distributed patterns. A significant positive association was found between social orienting and attention to the eyes across all participants ( p = 0.004), independent of age, sex, and diagnosis. These findings show that initial social orienting and later fine-grained social attention are linked at the individual level, supporting an integrated multi-level model of social perception. Preferential looking differences in ASD extend beyond early childhood, and the results reveal within-subject coherence across levels of social processing. Substantial inter-individual variability further supports a dimensional organization of social perception across development. Even though the cross-sectional design precludes conclusions about developmental trajectories and heterogeneity in cognitive and language abilities was not accounted for, together, these findings provide a framework for linking behavioral markers of social perception to underlying neurodevelopmental mechanisms.