Motor origins of tool use.

The current study examines the developmental trajectory of banging movements and its implications for tool use development. Twenty (6- to 15-month-old) infants wore reflective markers while banging a handled cube; movements were recorded at 240 Hz. Results indicated that through the second half-year, banging movements undergo developmental changes making them ideally suited for instrumental hammering and pounding. Younger infants were inefficient and variable when banging the object: Their hands followed circuitous paths of great lengths at high velocities. By 1 year, infants showed consistent and efficient straight up-down hand trajectories of smaller magnitude and velocity, allowing for precise aiming and delivering dependable levels of force. The findings suggest that tool use develops gradually from infants' existing manual behaviors.