The Role of Motor Coordination in the Facial Expression of Emotion in Autism Spectrum Disorders

Background: Deficits in emotional functioning have consistently been acknowledged as a primary characteristic of autism spectrum disorders (ASD) since Kanner’s original description in 1943. Given that emotional cues are an important component of social interaction, impairments in the understanding and expression of emotion have the potential to have significant ramifications for social-communicative functioning. A growing body of literature exists on the perception and recognition of emotional expressions in ASD, but comparatively fewer studies have investigated how individuals with ASD express emotion. These studies have relied largely on parental report, observations of young children within social interactions, and subjective coding systems of emotional expressiveness. The present study aimed to address a gap in the literature in this area by quantitatively measuring and characterizing facial movement during a controlled emotional expression task.

Objectives: The primary purpose of this study was to objectively examine facial movement in children and adolescents with ASD and their typically developing peers during a facial imitation task.

Methods: Participants were typically developing children and adolescents (n=28) and children and adolescents with ASD (n=29). Groups were well-characterized and matched on age, gender, and intellectual ability. Exclusion criteria included any comorbid neurological or psychiatric disorders that could affect facial motility or emotional functioning. Reflective markers were placed on facial landmarks corresponding to key muscles involved in facial expression. Participants observed a video of a model making various facial expressions, and were asked to imitate those expressions. Movement in both the X and Y coordinate directions was captured for each marker, and was then analyzed using an automated tracking software system (Vicon Motus). Both meaningful (e.g., happy, mad) and non-meaningful (e.g., scrunching eyebrows, showing teeth) expressions were examined. After participants completed the imitation task, naïve raters were asked to watch videotapes of their expressions and provide qualitative ratings. The relationship between facial movement and viewers’ ratings was then assessed.

Results: Preliminary analyses indicate that global patterns of muscle movement at the time of maximum facial displacement are largely similar in individuals with ASD and typically developing controls. However, the data suggest group differences in how particular regions of the face move as an expression unfolds over time (including movements at expected locations, as well as those not commonly associated with a certain expression). Preliminary data also point to a relationship between facial movement and the clarity with which an expression is perceived.

Conclusions: Children and adolescents with ASD seem to move the regions of their face in quantitatively different ways relative to their typically developing peers. This is suggestive of impairments in emotional expression in ASD, even among high-functioning individuals. Importantly, differences appear to occur at localized regions and time-points, rather than globally. This underscores the importance of fine-grained analyses of facial movement and emotional expression in this population.