KINEMATIC ANALYSIS OF PREHENSION MOVEMENTS IN CHILDREN

The kinematics of the reach-to-grasp movement were analyzed in ten hea lthy children (age 6-7 years) under different experimental conditions: distance and size of the target objects, and visual feedback during t he reach were varied in a within-subjects design. To assess age-relate d differences, the same experiments were performed in ten healthy adul ts. The experimental set-up was scaled according to body proportions t o obtain equivalent conditions for both age groups. The temporal coupl ing between the transport and grasp components of prehension was very similar in children and adults. Peak transport velocity increased by t he same factor in both age groups when the object distance was doubled . However, the decelerating approach phase was shorter in the children , who opened their hands relatively wider than adults. Unlike the adul ts, children failed to scale their grip aperture according to object s ize when visual feedback during the movement was lacking. The grip ape rture increased with object distance in adults, but not in the childre n. The intrasubject variability of kinematic parameters was distinctly higher in the children. The results suggest that grip formation is no t yet mature at an age of 6-7 years, depending more on visual feedback than in adult prehension. (C) 1998 Elsevier Science B.V. All rights r eserved.