"They found that babies aged seven months can differentiate voices from other sounds - even when they cannot see the person speaking.
By the age of 11 months, before they can speak themselves, the children have already learned to differentiate their mother tongue from other languages, the scientists discovered.
The American research team monitoring the brain waves of babies while playing them a series of recorded words in different languages.
The paper, published in the Proceedings of the National Academy of Sciences, said: ‘Based on the present study’s results, we speculate that motherese speech, with its exaggerated acoustic and articulatory features, particularly in one-on-one settings, enhances the activation of motor brain areas and the generation of internal motor models of speech.’
The babies’ neural activity suggest the part of the brain used to speak is already working before a child learns to talk.
Professor Patricia Kuhl, who led the project, said: ‘Most babies babble by seven months, but don’t utter their first words until after their first birthdays.
‘Finding activation in motor areas of the brain when infants are simply listening is significant, because it means the baby brain is engaged in trying to talk back right from the start and suggests that seven-month-olds’ brains are already trying to figure out how to make the right movements that will produce words.’
Professor Kuhl said that the exaggerated ‘goos’ and ‘gaas’ that parents speak to their babies are very important.
‘When infants hear it, their brains may find it easier to model the motor movements necessary to speak,’ she said.
‘Hearing us talk exercises the action areas of infants’ brains, going beyond what we thought happens when we talk to them.
‘Infants’ brains are preparing them to act on the world by practising how to speak before they actually say a word.’
