Comparing internal representations of facial expression kinematics between autistic and non-autistic adults

Abstract

Recent developments suggest that autistic individuals may require static and dynamic angry expressions to be of higher emotional intensity in order for them to be successfully identified. In the case of dynamic stimuli, autistic individuals require angry facial motion to have a higher speed. Therefore, it is plausible that autistic individuals do not have a ‘deficit’ in angry expression recognition, but rather their internal representation of these expressions is characterized by very high-speed movement. In this (pre-registered) study, 25 autistic and 25 non-autistic adults matched on age, gender, non-verbal reasoning and alexithymia completed a novel emotion-based task which employed dynamic displays of happy, angry and sad point light facial (PLF) expressions. On each trial, participants moved a slider to manipulate the speed of a PLF stimulus such that it moved at a speed that, in their ‘mind’s eye’, was typical of happy, angry or sad expressions. Results showed that participants attributed the highest speeds to angry, then happy, then sad, facial motion. Participants increased the speed of angry and happy expressions by 41% and 27% respectively and decreased the speed of sad expressions by 18%. This suggests that participants have ‘caricatured’ internal representations of emotion, wherein emotion-related kinematic cues are over-emphasized. There were no differences between autistic and non-autistic individuals in the speeds attributed to full-face and partial-face (those only showing the eyes or mouth) angry, happy and sad facial motion respectively. Consequently, we find no evidence that autistic adults possess atypical fast internal representations of angry expressions.