Toward a Cross-Species Measure of Social Motivation: Social Attention during Object Engagement in Autism and Williams Syndrome

Background: Autism Spectrum Disorder (ASD) is characterized by social deficits including reduced social orienting. According to the social motivation hypothesis of autism, this may be due to children with ASD finding social stimuli and interactions less inherently rewarding than typically developing individuals. Conversely, children with the genetic disorder Williams Syndrome (WS) are often hypersocial, suggesting they may find social interaction more rewarding than their typically developing peers. In a recent study examining the social motivation of domesticated dogs as compared to wolves, attentional bias to social stimuli was quantified by presenting animals with a highly engaging object and coding for looks toward the experimenter (vonHoldt et al. 2017). Interestingly, the greater social attention in dogs was associated with structural variants in several genes implicated in WS (vonHoldt et al. 2017), suggesting that attention to social vs. nonsocial stimuli represents a conserved aspect of social motivation across species. Therefore, measurement of this behavior in humans could serve as an informative correlate for future genetic studies of social motivation and its role in the development of ASD.

Objectives: Here we have developed a novel method to assess social motivation in children with ASD and WS, by quantifying their social attention while the child plays with a high-value toy, a competing non-social stimulus.

Methods: We analyzed video clips from the free play section of the Autism Diagnostic Observation Schedule (ADOS), a standardized, semi-structured, play-based interview often used to diagnose ASD. Specifically, we focused on brief segments when the child was actively engaged with a high-value object (an interactive musical toy), and coded the frequency and duration of the child's gaze toward the object, the examiner, and the caregiver. Inter-rater reliability was high (ICC > 0.9). Videos were coded for three groups: a typically developing group, a group with ASD, and a group with WS.

Results: In a small pilot sample (n=6 per group), we found that toddlers with ASD spent significantly less time looking at social partners (caregiver and examiner) compared to typically developing children during periods of engagement with the high-value toy (see figure). While typically developing children frequently alternated their gaze between the toy and social partners, children with ASD looked toward the adults much less frequently. Children with WS were more variable in their social attention, with some behaving more like children with ASD and others more like typically developing children. There was no significant difference in duration of play with the high-value toy across groups, suggesting that it was consistently engaging for all children.

Conclusions: We are currently replicating these findings in a larger dataset which includes both high-risk and low-risk typically developing children, as well as additional ASD and WS participants. Our pilot analyses suggest that a brief behavioral measure pitting a high-value toy against the innate draw of social engagement could serve as a rapid, feasible measure of social motivation, with implications for enhanced clinical assessment and behavioral phenotyping for genetic research in ASD and WS.