The Development of Motor Coordination in Infancy: Intercepting a Rolling Ball

Abstract

Interception skills were fundamental to human ancestors and remain critical to numerous daily activities in modern life. Successfully intercepting a moving object requires the sophisticated integration of perception, prediction, and motor control. While programming interception tasks in robotic design remains challenging, human adults perform these coordinated movements seamlessly in real-time. However, how these skills develop in the first place remains less understood. The current study investigated the development of interception skills in 11- to 24-month-old walking infants. Infants chased and contacted a remote-controlled ball rolling away from them in a straight trajectory at four constant speeds. Results suggest that 11- to 24-month-olds perceive ball catchability, as they attempted the task less frequently in response to higher ball speeds. However, they still attempt optimistically regardless of walking experience. Infants can intercept a moving ball through coordinated actions as soon as they learn to walk when the ball moves at a slow enough speed. At higher ball speeds, walking experience predicts success. Beyond faster walking speeds, more experienced infants better coordinate their movements. Consequently, infants with more walking experience have a larger temporal window to adjust their movements in real-time and make corrective attempts following a failure. Infants also employ different contact strategies. As ball speed increases, contacting the ball with the feet becomes the predominant strategy. However, more walking experience facilitates successful hand contacts while walking, which is a more complicated action, at higher ball speeds. In addition, infants who exhibited more flexibility in switching between contact strategies across trials were more successful. However, behavioral flexibility does not correlate with walking experience, suggesting that less experienced infants may benefit from using alternative strategies.