Mario Costantino¹ (), Bat-Sheva Hadad², Maryam Vaziri-Pashkam³, Erez Freud¹; ¹Department of Psychology, York University, ²Department of Special Education, University of Haifa, ³Department of Psychological and Brain Sciences, University of Delaware

Humans are adept at predicting the actions of others by interpreting subtle preparatory movements, a skill crucial for successful social interactions. This study investigated whether autistic individuals, who face challenges in social interactions, exhibit reduced efficiency in predicting others' actions. Additionally, we examined whether autistic individuals demonstrate improved understanding of the actions of other autistic individuals. To address these questions, we used a competitive-reaching task in which an "attacker" was directed by an auditory cue to move toward one of two possible targets. A "blocker" anticipates the attacker’s trajectory to reach the same target as quickly as possible. Using motion-tracking technology, we measured the blockers' finger reaction time (fRT), the time interval between the attacker’s movement initiation and the blocker’s response, as well as the blockers' movement velocity. Results reveal that autistic blockers have longer fRTs and slower velocities compared to non-autistic blockers, indicating a deficit in action prediction. This impairment is consistent regardless of the attacker’s identity, challenging the hypothesis that autistic individuals are better at predicting the actions of others autistic individuals. Importantly, a control experiment measured the blockers' reaction time in response to an auditory cue rather than to another person's action. This experiment revealed no differences between autistic and non-autistic blockers, suggesting that the observed differences in the main task were specific to action prediction. Taken together, these findings provide novel evidence of reduced efficiency in integrating perceptual cues critical for predicting others' actions, offering insights into the mechanisms underlying social interaction challenges in autism.