DEVELOPMENT OF SITTING AND REACHING IN 5-MONTH-OLD TO 6-MONTH-OLD INFANTS

Three studies are reported, investigating changes in body engagement b y 5- to 6-month-old infants as they reach for objects in the environme nt. Infants are distinguished and compared based on their relative abi lity to maintain a sitting posture without any external body support. The first study demonstrates that manual reaching by sitter infants is coordinated with forward leaning of the trunk, whereas reaching by no nsitters is not. The second study demonstrates that nonsitter infants provided with hip support also show signs of a coordination between re aching of the hand and forward leaning of the trunk. The third study c ompares nonsitter, nearsitter, and sitter infants as they reach for mu ltiple objects spread across their prehensile space. Results demonstra te expansion in the mapping of infants' prehensile space and hand use as a function of self-sitting ability. The reported results are discus sed as expressions of the interaction between the development of postu ral, perceptual, and action systems in infancy.