Movement-Related Differences Between Infants with High and Low Likelihood of Autism: A Longitudinal Study Using Markerless Motion Tracking.

Background: Motor behaviour has been shown to differ in both complexity and variability between neurotypical and autistic populations. However, there is little research on the early development of specific kinematic features and their timing of emergence in early life. Methods: The current study examined the early development of kinematic features (duration, range, velocity, acceleration, entropy, and jerk) in infants with a high or low likelihood of autism using state-of-the-art automatic pose estimation models. We evaluated weekly home-recorded videos of naturalistic, spontaneous movements (controlling for clothing, background, and posture) from 60 participants (705 videos) longitudinally over the first six months of life. We automatically extracted kinematic data, including motion of the shoulders, elbows, hips, and knees. Results: Of the kinematic features examined, we found that the groups differed only in the variability of entropy, whereby the variability of entropy was lower in HL compared with LL infants across the first six months of infancy. Conclusions: These findings highlight the potential of non-invasive, home-based motion tracking to identify early divergences in infant motor trajectories among those with an elevated likelihood of autism.