How do object size and rigidity affect reaching and grasping in infants with Down syndrome?

Reaching and grasping skills have been described to emerge from a dynamic interaction between intrinsic and extrinsic factors. The purpose of the present study was to investigate the interaction between such an intrinsic factor, Down syndrome, and extrinsic factors, such as different object properties. Seven infants with Down syndrome and seven infants with typical development were assessed at the ages of 4, 5 and 6 months. The findings showed that object size influenced the kinematics of reaching for the infants with Down syndrome and the grasping frequency for the typical infants. The object rigidity was shown to have a major influence on grasping frequency.