Background: Limited monitoring of others’ activities and a lack of attention to faces are hallmarks of ASD in toddlers. Due to the congenital nature of ASD and its strong genetic component, it has been hypothesized that deficits in social perception might be present in the first months of life, and that even unaffected siblings might share some phenotypic similarities with their affected siblings.

Objectives: Visual scanning trajectories serve to obtain specific task-relevant information and are highly influenced by the perceptual and semantic content of the scene, and thus can be used to characterize deficits in social perception. This study examined action and speech monitoring in low risk (LR) infants and infants at high risk (HR) for ASD (siblings of children with ASD).

Methods: Participants included 10 LR and 18 HR 3-month-old infants. Infants were presented with two videos in which an actress: (1) spoke directly to the camera in motherese (“Speech”), or (2) engaged in making a sandwich (“Sandwich”). Visual scanning trajectories were recorded using an eye-tracker.

Results: In both video conditions HR infants, in comparison to LR infants, spent significantly more time examining objects and less attending to the actress. Notably, while LR infants modulated their attention to the face and hand area in accord with the actress’s activities, the distribution of visual attention in HR infants was less sensitive to the experimental manipulation.

Conclusions: These results suggest that delays in human action monitoring and attention to speech can be demonstrated within the third month of life in infants at risk for developing ASD. While relatively few children in HR group are expected to develop ASD, results from this study suggests that an innate or early-emerging perceptual mechanism that support detection and monitoring of behaviors in others is impaired in 3 month old infants at high risk for ASD.