Newborn infants produce coordinated stepping movements when held upright. Movements disappear at about 2 months and reappear at about 8-10 mo. Real walking emerges at about 12 mo. Behavior is sensitive to bodily and environmental parameters. Stepping can be elicited during the silent period if the baby is held upright in a warm bath.
Infants perform coordinated alternating steps when held upright on a motorized treadmill.
Adding weight to the legs of stepping infants stops them from stepping.