EXPRESS: Eye-tracking the production of counterfactual alternatives to narrative events in autistic adults.

Research has found atypical counterfactual production in autistic children, yet intact counterfactual reasoning in autistic adults. To date, however, no research has investigated counterfactual production in autistic adults. The current study combined a counterfactual production task with eye-tracking in the visual world paradigm to examine how autistic and neurotypical adults plan and initiate counterfactual responses. Autistic participants showed slower speech initiation and more disfluencies, consistent with broader speech production patterns, but did not experience greater difficulties with counterfactual production itself. Both groups also showed a comparable preference to produce additive counterfactuals, suggesting developmental convergence by adulthood. In contrast, while both groups showed a strong preference to produce and fixate human causes, this bias was stronger among neurotypical adults than autistic participants, who more often considered physical causes and were less influenced by salient social cues. Additionally, speech-locked eye movements revealed group differences: neurotypical adults flexibly modulated their gaze to human causes depending on whether they produced factual or counterfactual responses, whereas autistic adults showed more uniform gaze patterns across conditions. These findings highlight shared competencies but distinct social-cognitive strategies in counterfactual production across groups.