Adherence to the two-thirds power law and kinematic differences in children with autism during ellipse drawing and tracing activities on smart-tablet

Autistic individuals often demonstrate atypical motor control of purposeful action1, especially in the area of fine motor skills. • Studies assessing writing and drawing reveal larger peak velocities and greater sizing variability in autistic participants.2 • During swiping gestures on a tablet, those with autism show atypical kinematics compared to typically-developing (TD) controls.3 • The emergence of these atypical kinematic features require further investigation. • One method used to characterize motor control is the two-thirds power law (⅔ PL), a law of motion involving a covariation between the velocity and curvature, in which velocity decreases in more curved parts and increases in less curved parts of movement, as specified by the equation: • Tangential Velocity = K * Radius of Curvature1/3 • The ⅔ PL governs many types of human movement, including of the arm4, foot5 and eyes.6 • It is present in early in development7 and the velocity-curvature coupling appears to progress with age.8 • The goal of this study is to assess adherence to the ⅔ PL and kinematic features during drawing movements in autistic and TD children ages 4 through 8. • The law has yet to be studied in autism. • It may offer insight into atypical motor development and provide a better metric by which to assess motor kinematics.