Plantar response during infancy.

Cross-sectional as well as longitudinal studies on full-term urban and rural infants demonstrated that the initial extensor plantar response present in the first half of the infancy changed to a flexor plantar response in the later half. The urban infants receiving nutritional supplements showed an advance of 4 weeks over the rural infants. This process of change-over of plantar response was delayed in pre-term infants. However, two pairs of twins showed plantar response almost identical to full-term urban infants.