Positive Affective Response to Dynamic Smiling Faces in Young Children with Autism Spectrum Disorder

Background:  Children with Autism Spectrum Disorder (ASD) are able to show a full range of emotions (Braverman, Fein, Lucci & Waterhouse, 1989) but in social situations they reportedly display less positive affect than typically-developing (TD) children (Snow, Hertzif, Shapiro, 1987). For example, children with ASD were less likely to smile back in response to their mothers’ smiles (Dawson, Hill, Spencer, Galpert & Watson, 1990). Although this phenomenon has been observed in naturalistic settings, few studies have examined affective response to faces in experimental settings. High-functioning adults with ASD exhibited deficits in automatic mimicry of facial expressions when looking at static facial images (McIntosh, Reichmann-Decker, Winkeilman, Wilbarger, 2006). The current study aims to explore the effects of social and non-social dynamic stimuli on smiling in young children with ASD.

Objectives: To determine whether smiling differs in children with and without ASD while watching social and non-social stimuli. We hypothesized that the children with ASD would express fewer smiles than TD children, especially in response to dynamic faces.

Methods:  53 children (ASD, n=25, TD, n=28) between the ages of 20 and 78 months were shown a gaze-contingent eye-tracking experiment consisting of non-social (fractals) and social (faces) conditions. In the non-social condition, two fractal images were presented, one of which became dynamic when the child fixated gaze on it. Similarly, the social condition consisted of two neutral static faces one of which, when fixated upon, became dynamic and smiled. Each condition consisted of 128 trials. The child’s positive affect (smiles) was coded offline for both conditions. Proportion of trials with smiles was calculated based on the number of trials in which the child smiled divided by the number of trials the child watched. The ADOS-2 Module 1 was administered to all children with ASD and their parents completed the Vineland-II.

Results:  The ASD group expressed positive affect on 8.1% (SD=11) of face trials versus 5.2% (SD=11) of fractal trials, compared to 9.7% (SD=13) and 4.0% (SD=5), respectively, in the TD group. An ANOVA indicated a significant main effect of condition (F(1,47) = 4.92, p=.032), whereby both groups expressed more positive affect during the social than during the nonsocial condition, but no main effect of group (F(1,47)=37.45, p = .993). There was no group by condition interaction (p=.522). Furthermore, in the ASD group, smiles were significantly correlated with the Vineland-II Interpersonal V-Score (r=.519, p=.019) and with shared facial expressions on the ADOS-2 (composite score of the Responsive Social Smile and Facial Expressions Directed to Others items; r=.423, p=.044).

Conclusions:  Young children with ASD expressed positive affect at rates similar to TD children in response to dynamic smiling faces. Smiling seems to be an indicator of adaptive social behavior in ASD, as those who smiled more at the faces stimuli tended to have better interpersonal relationships with peers and were able to share a range of affect in naturalistic situations. This study shows that measuring affective response to dynamic stimuli can provide useful insight into real-world social behaviors.