Learning how to wave bye-bye is an important milestone for an infant that usually occurs between the age of 10 months and a year. A study in Pediatrics International found premature infants mastered the bye-bye gesture significantly later than full-term babies and used different hand and wrist motions.
Babies are born with an innate ability to imitate that develops throughout infancy. Research has shown this ability is controlled by circuitry in the brain that regulates the development of the visual and fine motor skills required to imitate others. The timing of bye-bye imitations and the type of hand motions used may be an important indicator of a premature infant’s developmental state, the researchers said.
The study in Japan compared bye-bye waving in 597 full-term and 95 premature infants, using their corrected age, or their age if they had been born full term. (Corrected age estimates a premature baby’s developmental age by subtracting the number of weeks the infant was premature from his chronological age.)
Mothers reported the age at which their babies started to wave bye-bye. The infants’ hand motions were analyzed from video recordings made at well-baby checkups, where researchers said goodbye to each infant orally and with hand motions.