Less differentiated facial responses to naturalistic films of another person's emotional expressions in adolescents and adults with High-Functioning Autism Spectrum Disorder

Background Reduced facial expressivity (flat affect) and deficits in nonverbal communicative behaviors are characteristic symptoms of autism spectrum disorder (ASD). Based on the important interpersonal functions of facial emotional responsiveness the present study aimed at a comprehensive and differentiated analysis of perceptible facial behavior in response to another person's naturalistic, dynamic facial expressions of emotion. Methods: In a group of 21 adolescent and adult individuals with High-Funtioning autism spectrum disorder (HF-ASD) and in 21 matched healthy controls we examined perceptible facial responses using the whole range of action units of the Facial Action Coding System (FACS) while participants were watching films displaying continuous, dynamic real-life facial expressions of four universal emotions (cheerfulness, anger, sadness, anxiety). The duration of the 80s films was in the typical range of casual face-to-face interactions. Results: Overall, the number of congruent facial muscle movements while watching the emotion-laden stimulus films did not differ in the two groups. However, the comprehensive FACS analysis indicated that participants with HF-ASD displayed less differentiated facial responses to the watched emotional expressions. Conclusions: The unusual or awkward patterns of facial emotional responses in ASD may hamper the recognition of affect in other people as well as the interaction partner's sense of interpersonal resonance, and thereby lead to social disadvantage in individuals with ASD.