Abstract
Typical development shows early biases in face attention during infancy, characterized by face inversion effects and increased attention to the left side of the face. In autism spectrum disorder (ASD), face scanning patterns often differ, with reduced inversion effects and left-side biases. The current study examined inversion effects, side biases, and pupil responses in EL and TL infants at 7, 10, and 13 months using linear mixed modeling. TL infants showed greater looking to the left side of the face than EL infants both over the full trial duration and in the 500-1000 ms trial window. Also, in the 500-1000 ms window, a significant left versus right side difference was observed only in the TL group. Pupil responses revealed an interaction between group and age, with EL infants showing a larger pupil size increase over time. These findings suggest that elevated ASD likelihood may be linked to early face-processing differences, such as reduced left gaze bias and greater pupil increases in infancy. Further research is necessary to determine if these patterns are specific to faces or reflect broader atypicalities in hemispheric asymmetry and autonomic function, and how these differences may contribute to later emerging features of ASD.