Pupil Dilation to Dynamic Audiovisual Emotional Speech Reflects Autistic-Trait Variation in Neurotypical Adults.

Autistic individuals commonly exhibit difficulties with emotion recognition, difficulties that contribute to social issues in Autism. Both emotion recognition and social abilities are distributed along a spectrum in Autism and the general population. We explored how Autistic traits, including social abilities, relate to emotional processing measured via pupil dilation in a neurotypical population. We presented participants with dynamic, audiovisual stimuli of actors uttering a semantically neutral phrase. These utterances were expressed with either a neutral tone of voice and facial expression, or with an angry, fearful, disgusted, happy, sad, or surprised tone and expression. Each emotion was presented with high- and low-intensity depictions. Participants were asked to identify the emotion and rate its intensity. Participants' pupillary responses were recorded during viewing. Traits associated with Autism were measured through a battery of self-report scales. We then tested for associations between Autistic traits and pupillary response to emotional stimuli. Broadly speaking, individuals with higher Autistic traits exhibited smaller overall pupillary responses to emotional stimuli. More specifically, this relation was driven by socio-communicative traits (Social Motivation, Social Knowledge). Further, social traits were especially correlated with physiological responses to low-intensity emotional presentation. This reflects previous studies suggesting that Autistic individuals show more pronounced difficulties with emotion recognition when emotional expression is more subtle. Finally, social Autistic traits were related to physiological responses to anger, fear, surprise, sadness and to a lesser extent happiness, but not disgust.