Attenuated behavioral interpersonal synchrony in autistic adults is not explained by perception of timing.

Attenuated interpersonal synchrony (IPS) has been shown between autistic individuals and their interaction partners; however, the mechanisms of this attenuation remain unclear. One possibility could lie in perceiving the timing of others' behaviors. The present study aimed to relate the behavioral production of IPS with the perception of temporal dynamics of social interactions and event timing perception in autistic and non-autistic adults. Autistic and non-autistic participants engaged in naturalistic conversations with a non-autistic stranger, who was naïve to the participant's diagnostic status. Behavioral IPS was computed using automatic video-based analysis. Participants reported their experiences of perceived IPS with the partner, as a measure of the perceived temporal dynamics of the social interaction. A perceptual simultaneity task measured the perception of event timing in a nonsocial context. Bayesian linear mixed models were used to evaluate the effects of perceived IPS ratings and simultaneity thresholds on behavioral IPS. Expectedly, behavioral IPS was reduced for dyads including an autistic adult. Neither perceived IPS ratings, nor simultaneity thresholds, were associated with reduced behavioral IPS for dyads with or without an autistic adult. These findings hint that attenuated behavioral IPS may not result from atypical perceived timing of others' behaviors or event timing perception.