Automatic facial responses to briefly presented emotional stimuli in autism spectrum disorder

•The ASD group failed to differentiate by valence in zygomaticus and corrugator EMG.•Brief emotions do not sufficiently engage mimicry system in high-functioning ASDs.•Pre- and post-stimulus arousal (SCL, SCR) were atypical with stimulus repetition.•Typical ECD suggests individuals had intact stimulus registration/detection.•Disruption in allocation of attention to faces provides a target for interventions. Emotion processing, including automatic facial mimicry, plays an important role in social reciprocity. Disruptions in these processes have implications for individuals with impaired social functioning, such as autism spectrum disorders (ASDs). Past research has demonstrated that ASDs are impaired in the recognition of briefly presented emotions and display atypical mimicry of emotions presented for protracted duration. Mimicry (electromyography; EMG) of briefly presented emotions was investigated in adults with ASDs. Concurrent measures of skin conductance and cardiac responses were used as markers of orientation and stimulus detection, respectively. A backward masking task was employed whereby the emotional face (happy, angry) was presented for 30ms followed by a neutral face “mask”. An implicit comparison task required rapid gender identification. The ASD group failed to differentiate by valence in their EMG (zygomaticus, corrugator) and demonstrated atypical pre- and post-stimulus arousal. These findings may provide a potential mechanism for marked deficits in social reciprocity.