Babies may learn to speak in the same way birds learn to sing, scientists believe.
Babies respond best to feedback
Previous studies have shown that many birds learn to sing through social interaction and feedback rather than by simply imitating others.
For example, adult female cowbirds, which do not sing, use social gestures and displays to encourage particular song qualities in young males.
Now research in the United States suggests infants learn to speak in much the same way.
Infants at play
Michael Goldstein and colleagues at Franklin & Marshall College in Pennsylvania studied eight-month-old infants and their mothers in play sessions.
During the first part of the study the researchers monitored how often the babies made vocal noises and how their mothers reacted to each vocalisation.
Later the mothers' responses were manipulated. Half the mothers were allowed to respond to their infants' baby noises by smiling, moving closer and touching their children.
The other half, while paying as much attention to their offspring, could not synchronise their responses with vocalisations.
After analysing recording of the babies' babbles, the researchers found that noises from the first group developed faster during the play session.
Their sounds contained more syllables and faster consonant to vowel transitions than those of babies in the second group.
Writing in the journal, Proceedings of the National Academy of Sciences the researchers said: "These data are empirical evidence of a parallel in function between vocal precursors of songbirds and infants.
"Because imitation is usually considered the mechanism for vocal learning in both taxa (species), the findings introduce social shaping as a general process underlying the development of speech and song."
Dr Alan Slater, a reader in psychology at Exeter University, backed the findings.
"This is a complex area but what they are claiming has to be true. If you had infants who were not given any encouragement when they are speaking then their language development would be delayed."
He said providing infants with feedback is the best way to ensure they learn to speak when they are supposed to.
Dr Slater said: "The best advice is to provide infants with a lot of verbal feedback and to talk to children in a manner that is called infant directive speech.
"This means that you should not talk to them about the state of Iraq, for instance, but rather about what is happening in the here and now, for instance when parents are taking off their clothes."