Orienting to social and non-social stimuli in the early broader autism phenotype

Background: A growing number of studies with infant siblings of children diagnosed with ASD have revealed early behavioural differences in the broader autism phenotype, allowing for a prospective approach to the study of the emergence of autism in infancy.

Objectives: In view of previous findings of atypical eye gaze tracking in children and adults with autism and more recently, in relatives of individuals with autism, the aim of this study was to examine the early autism phenotype in infant siblings of children diagnosed with ASD (Sibs-ASD) compared to controls (Sibs-TD), using the TOBII 1750 eye-tracking system.

Methods: A group of 20 Sibs-ASD (11 females) was compared to a group of 20 controls (10 females) between 6 and 9 months on a free-viewing task displaying static images of social (e.g. faces) and non-social (e.g. cars) stimuli. An eye tracking system (TOBII 1750) was used to register the gaze of the participants.

Results: The two groups did not differ in a number of gaze behaviours including a larger number of fixations and longer durations spent looking at faces, relative to competing stimuli. On the other hand, there was a tendency for some sib-ASD infants to show longer latencies to orient toward faces.

Conclusions: The results suggest differences in orienting toward faces in a subgroup of infant siblings of children with autism. These differences are likely to relate to the broader autism phenotype in this condition and potentially to the emergence of clear symptoms in subsequent years in some infants.