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Infants can tell the difference between sounds of all languages until about eight months of age, according to a new study. After eight months, their brains start to focus only on the sounds they hear around them. 

Researchers are yet to explain the transition, but social interactions and caregivers' use of exaggerated "parentese" style of speech seem to help.

According to the study, 7- and 11-month-old infants stimulate areas of the brain that coordinate and plan motor movements for speech. Babies also start laying down the groundwork of how to form words long before they actually begin to speak, the study found.

"Most babies babble by seven months, but don't utter their first words until after their first birthdays," said lead author Patricia Kuhl, who is the co-director of the UW's Institute for Learning and Brain Sciences, in the press release. "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 7-month-olds' brains are already trying to figure out how to make the right movements that will produce words."

Researchers believe this practice at motor planning contributes to the transition when infants become more sensitive to their native language. 

"Hearing us talk exercises the action areas of infants' brains, going beyond what we thought happens when we talk to them," Kuhl said. "Infants' brains are preparing them to act on the world by practicing how to speak before they actually say a word."

The findings of the study emphasize the importance of talking to kids during social interactions even if they aren't talking back yet. 

The study has been published in the Proceedings of the National Academy of Sciences.