Marked impairment in the use of eye-to-eye contact and attention to human faces (Trepagnier & Sebrechts, 2002) typical of Autism Spectrum Disorders (ASD) was reported to appear early in development (Osterling & G.Dawson, 1994). Recent efforts have thus been directed to document these atypicalities in very young children so as to gather information on the origins of deficits in social communication in the ASD.
Eye-tracking systems have proved particularly useful for systematically assessing gaze behavior of children with ASD in the above contexts. While the majority of these studies focused on foveal vision, recent evidence suggests that eccentric vision is used actively by children with ASD to optimize what is perceived with difficulty (Mottron_et_al., 2007).
To decipher the complementary role that foveal and excentric vision play when looking at faces, we explored eye-gaze peculiarities in children with ASD using a novel eye-tracking device that allows monitoring in conjunction foveal and peripheral vision and this in naturalistic settings, (in contrast to most eye-trackers that oblige the child to watch a computer screen). Studying eye-gaze behavior in a naturalistic social interaction was thought to be crucial, as social deficits of children with ASD are more pronounced in everyday settings than in experimental tasks (Klin_et_al., 2002a ; Nadel & Butterworth, 1999).
A group of 13 ASD children (4 female, 9 male, age 3-10) diagnosed with DSMIV-R (APA, 2000) and ADI-R (Lord_et_al, 1994) and presenting mild to severe autism (M=40.4- 6.9, range=29-47) was compared to a group of 13 typically developing (TD) children, matched on developmental age (1.6–4.3 dev. Age), as measured by Vineland Adaptive Behavior Scales (Sparrow, Balla, & Cicchetti, 1984).
For the two groups of children, the task consisted of a 20-30 minutes play session with the child’s caretaker (blowing soap bubbles and creating forms with play-doh) .
The child’s gaze was monitored via a novel eye-tracking device consisting of a camera-on hat that records what the child can see and what (s)he actually looks at. Eye-gaze peculiarities were quantified by measuring the number, duration and frequency of gaze fixations at the other person in both foveal and eccentric vision. For each of these measurements, the effect of group diagnosis ( ASD/ control), gender, chronological age and developmental age was assessed through a four-way anova.
Children with ASD dramatically differed in their gaze strategy from the TD children. The ASD group looked less frequently (p<0.000001), less longer (p<0.0002) at the other and, when they did, they looked often through lateral glances, i.e. the face of the adult tended to appear on the periphery of their broad field of view. The differences were found to be independent from the severity of the disorder, chronological and developmental age and gender.
These findings suggest that precise measurement of the frequency, duration and directionality of gaze towards faces are robust indicators of ASD and, as such, may provide quantified information to complement clinical observations and confirm the prevalent use of eccentric vision from fovea in children with ASD (Ritvo et al., 2009).