Development of visual center of mass localization for grasp point selection

Adults assess precisely the center of mass (CM) of single-bodied objects and choose grasping points that span an axis through or close to the center of mass when lifting them. The present study examined how children and adults assess the CM when lifting two-bodied objects (barbells) and how this ability develops. Four- to five-year olds, 6- to 7-year olds, 9- to 11-year olds and adults were required to grasp and lift symmetrically and asymmetrically proportioned miniature barbells and their grasping points were recorded. While the 4- to 5-year olds grasped near the center of the barbell, accuracy of assessing the correct CM improved linearly with age. Although adults grasped close to the CM, their CM determination follows only an approximation of the physical law.