Emily Fewster¹ (), Bat-Sheva Hadad², Erez Freud¹; ¹Department of Psychology, Centre for Vision Research, York University, ²Department of Special Education, University of Haifa

Autistic individuals often exhibit differences in perceptual and visuomotor functioning. One account for these alterations suggests that autism involves reduced specialization of cortical systems. In the current study, we investigate the extent to which handedness, one of the most robust markers of cerebral lateralization, is modulated in autistic individuals. While previous studies already demonstrated more cases of left-handedness and reduced right-handed specialization in autism, those studies primarily relied on self-reports and questionnaires. Here, we employed a naturalistic task to explore this topic. Autistic and non-autistic right-handed participants (27 in each group) recreated five Lego models using blocks placed on a standardized tabletop. This design allowed us to capture dynamic, real-world visuomotor behaviours and explore how autistic individuals use their right and left hands to explore and act on their reaching space. Our results revealed key group differences. First and most importantly, autistic participants displayed a lower proportion of right-hand grasps, suggesting reduced lateralization. Second, we observed differences in the use of 3D space, with autistic participants showing a stronger preference for blocks closer to their hands, suggesting larger safety margins in visuomotor interactions with the surrounding 3D environment. Finally, autistic participants completed the task slower than non-autistic participants, indicating differences in motor efficiency. Taken together, these findings demonstrate reduced specialization of hand use in autism, which may contribute to challenges and differences in visuomotor control.