Prehension in children and adults: The effects of object size

Studies of visually goal-directed arm movements in adults have shown that v arious task constraints such as intention, context, and object properties a ffect different kinematic characteristics of the movement components (Jeann erod, 1984; MacKenzie et al., 1987; Marteniuk et al., 1987, 1990; Paulignan et al., 1991; Soechting, 1984). The purpose of the present study was to co mpare the effects of varying object size on the kinematics of reaching and grasping in both children and adults. Five children aged 9-10 years and fiv e adults aged 18-24 years reached for and grasped three different sized cub es. Results revealed that object size had the same effect on the planning a nd control of reaching and grasping movements in children as in adults. Unl ike adults, however, children in this age range spent more time in decelera tion and reached peak aperture much later in the movement trajectory. The r esults were interpreted as immature integration of the visual and proprioce ptive systems in 9-10 year olds. The implications of these findings for fur ther examining developmental trends in prehension are discussed. (C) 1998 P ublished by Elsevier Science B.V. All rights reserved.