When babies babble and make sounds, parents respond to them sometimes with words but also with expression, gesture and encouragement. This is similar to certain songbirds whose mothers encourage and respond to their singing using movement.
By learning about and responding to these social cues, babies (and baby birds) practise their babbling sounds. When doing this they then develop more sophisticated ways of communicating and enjoying social company.
So, next time you hear your baby babbling, remember that any response from you is a wonderful thing. Smiling, nodding, moving in time with their voice and responding with an action are just as valuable as talking back.
References:
[1] Goldstein M.H, King A.P, West M.J. (2003). ‘Social interaction shapes babbling: Testing parallels between birdsong and speech’. Proceedings of the National Academy of Sciences Vol.100:13.
Available online: https://pubmed.ncbi.nlm.nih.gov/12808137/