Heart rate defined sustained attention relates to visual attention in autism and fragile X syndrome.

Social attention, including shared attention and social orienting, is essential for positive social interactions. Although early visual social attention is often quantified using eye tracking, these indices may not consistently reflect cognitive engagement. Heart rate defined sustained attention (HRDSA) is a physiological measure that can index cognitive engagement alongside visual attention, leading to more comprehensive assessments of attentional processes that are particularly important in young, neurodiverse children with high support needs, including those with autism and fragile X syndrome (FXS). The present study examined visual and heart-defined measures of social attention to the Selective Social Attention task, a video-based assay of social attention, in children with autism, FXS, and neurotypical development. Linear mixed models examined group and condition effects in multiple cardiac indices and overall looking at the scene. Findings suggest that, overall, children across all groups engaged similarly across the experiment in most dimensions of HRDSA, and consistent with previous work, autistic children spent less time visually attending to the scene than either other group. HRDSA was positively associated with visual social attention. Combining physiological and visual attention measures may elucidate the complex nature of social attention and be especially valuable for neurodiverse children when typical assessments are inaccessible.