Specificity of Social Visual Engagement Patterns in Toddlers with Autism Spectrum Disorder and Williams Syndrome

Background: The social phenotypes of Autism Spectrum Disorder (ASD) and Williams Syndrome (WS) are often contrasted with one another (Bellugi, 2001): in general, individuals with ASD are characterized as possessing reduced social interest, whereas those with WS are characterized as atypically prosocial and initiating. The present study seeks to investigate patterns of social visual engagement in groups of toddlers with ASD or WS. By gathering information about where a young child looks, we also gather information about his or her cumulative social experience and interests. Contrasting groups of young children with ASD and WS—both affected by social disability, but in seemingly opposite ways—allows unique insight into distinct, possibly disorder-specific avenues of early social development. Thus, by quantifying patterns of social visual engagement, we can further broaden our understanding of the specificity of early social disability in individuals with ASD.

Objectives: To quantify profiles of social visual engagement in toddlers with distinct diagnoses (ASD, WS, or non-ASD developmental delays (DD)) relative to a comparison sample of typically developing (TD) toddlers.

Methods: Twenty-four-month-old children were eye-tracked while viewing video scenes of naturalistic caregiver interactions. Diagnoses were made by experienced clinicians blind to experimental eye-tracking data, with genetic testing to confirm the WS deletion. All participant groups were matched on chronological age. Percentage of fixation time to 4 regions of interest (eyes, mouth, body, and object) were calculated for each participant. Fixation patterns were compared between groups using two-tailed independent samples t-tests.

Results: Toddlers with WS fixated significantly more on eyes compared to the ASD, DD, and TD groups (all p’s < 0.01, Figure 1a). By contrast, toddlers with ASD exhibited a trend toward less time spent looking at eyes compared to all other toddler groups (p=0.094, Figure 1a). Toddlers with WS also fixated significantly less on the mouth region relative to all other groups (all p’s < 0.01, Figure 1b). Toddlers with ASD showed a trend towards increased fixation on the body region relative to TD toddlers (p=0.057, Figure 1c). Finally, both ASD and WS groups spent more time looking at objects relative to TD toddlers (both p’s < 0.05, Figure 1d).

Conclusions: Data from ASD and WS toddlers reveal marked and group-specific deviations from the fixation patterns observed in typical development. Toddlers with WS display a striking preference for looking at the eyes of others, whereas toddlers with ASD trend towards less eye-looking. In short, although toddlers with ASD share aspects of social and intellectual disability with WS and DD cohorts, respectively (see clinical characterization scores in Table 1), our results reveal the specificity of reduced eye-looking to the social phenotype of ASD, as well as aspects of atypical social visual engagement—such as increased attention to objects—that may be common to developmental delays characterized by social disability. These results highlight distinct mechanisms by which developmental outcomes precipitate in ASD and may ultimately point toward different paradigms of treatment for young children with Autism Spectrum Disorder.