Individuals with autism have difficulties learning implicit sequences of social interactions that require mentalizing.

Purpose: This research investigated implicit social sequencing in adults with Autism Spectrum Disorder. Previous research emphasized the role of the cerebellum in autism, and in processing action sequences within social contexts requiring mental state attribution (mentalizing). We therefore hypothesized that individuals with autism would show reduced implicit sequencing in an interactive negotiation game that involves mentalizing. Methods: Participants included 20 adults with autism and 20 matched healthy controls. Using a novel ultimatum serial reaction time task, participants received offers for a division of 10 points from multiple proposers and responded as quickly as possible. Unbeknownst to the participants, offers were presented in repeated or random sequences. Additionally, the proposers' implied traits (egocentric versus generous offers) and the volatility of their offers (variable versus stable) were varied to assess context effects on implicit sequencing. Results: As expected, autistic participants revealed no significant speed differences between repeated and random sequences, while controls were faster in repeated sequences. Considering context effects, both groups were faster in repeated sequences when offers were stable (i.e., identical across trials). Conversely, when offers were volatile, responses slowed down under repeated sequences. Conclusion: Findings suggest reduced implicit social sequencing capacities in adults with autism. Social context factors influenced learning in both groups, indicating that autistic individuals may either perform at typical social levels when statistically controlling for their reduced sequencing capacities, or may sufficiently compensate under explicit task instructions. These results highlight social sequence learning as a promising target for intervention in training programs for autistic individuals.