Infant hand-use preferences for grasping objects contributes to the development of a hand-use preference for manipulating objects

Twenty-five infants, divided into three approximately equal groups according to their hand-use preference for reaching for and grasping objects (right, left, or no-preference), were videotaped at 7 and 11 months while involved in a semiplay activity in which they were presented with 26 toys (20-40 s for each presentation). Unimanual manipulation activity was coded, and the increase or decrease in preferred hand use across the two ages was analyzed. Infants with a right preference for reaching showed an increase in right-hand use for unimanual manipulatory actions from 7 to 11 months. Infants with a left preference for reaching showed an increase in left-hand use whereas infants with no preference for reaching showed a modest increase in the use of the right hand. These results support a modified progressive lateralization theory, which posits that a hand-use preference for reaching for and grasping objects will concatenate during development into a hand-use preference for manipulating objects.