Washington: The repetitive babbles of babies primarily are motivated by the infants' ability to hear themselves, shows a US study.

"Hearing is a critical aspect of infants' motivation to make early sounds," said study author Mary Fagan, an assistant professor of communication science and disorders in the University of Missouri-Columbia School of Health Professions.

"The fact that they attend to and learn from their own behaviours, especially in speech, highlights how infants' own experiences help their language, social and cognitive development," she added.