Posture Matters: Object Manipulation During the Transition to Arms-Free Sitting in Infants at Elevated vs. Typical Likelihood for Autism Spectrum Disorder.

Aims: We investigated how infants grasped and transferred toys over a four-week period as they transitioned to arms-free sitting. We compared object manipulation in infants with typical likelihood (TL) and elevated likelihood (EL) for autism spectrum disorder (ASD) as they sat with vs. without support.
Methods: Eighteen infants (7 EL; 11 TL; 5-8 months of age at the start of the study) were observed during three sessions at home across the transition to arms-free sitting. At each session, toys were presented to the infants in two different postures: sitting with support from a boppy pillow and sitting independently. Mean percentage of time spent grasping and rates of transferring objects between two hands were calculated for each infant at each session.
Results: Both grasping time and transfer rate increased across the transition to arms-free sitting. EL infants, but not TL infants, spent significantly less time grasping toys when sitting independently than when sitting with support.Conclusions: Sitting plays a significant role in the development of object manipulation skills. Our results reveal a need to examine object manipulation skills in multiple posture contexts, especially in infants who exhibit motor delays.