Body scale and the development of prehension.
This study examined whether common dimensionless ratios define the critical point in the shifts in the grip coordination pattern of preschoolers and adults engaged in a displacement grasping activity with cubes that varied in object size. The findings indicated that there was an interaction between task constraints and organismic constraints in determining the grasping pattern utilized. However, when the object size is scaled to hand size there are common dimensionless ratios that correspond to the grasping patterns and the limb orientations employed across the age range utilized. Furthermore, 5 grip configurations accounted for the majority of grip variance in both age groups. The findings suggest a strong role for the impact of body scale on the development of coordination and provide preliminary evidence for the view that the development of prehension is a reflection of the constraints imposed on action.