Three studies are reported, investigating changes in body engagement by 5-to 6-month-old
infants as they reach for objects in the environment. Infants are distinguished and compared
based on their relative ability 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 nonsitters is not. The second study
demonstrates that nonsitter infants provided with hip support also show signs of a …