Infants who can't yet speak themselves are able to recognize that people who speak different languages use words differently, according to New Zealand research.

A study at the University of Auckland found that infants as young as 13 months understood that people from different linguistic communities used different words to refer to the same object.

"This is the first evidence that infants do not indiscriminately generalize words across people," study co-author Dr Annette Henderson said in a statement.

"This early appreciation might help infants by encouraging them to focus on learning the words that will most likely be shared by members of their own linguistic group."

The researchers tested whether infants understood that word meanings (object labels) were not shared by individuals who speak different languages by showing infants from English-speaking families video clips that introduced two actors: one speaking French and the other English.

They then monitored how long each infant looked at objects after the objects had been labeled by each actor, as infants looked longer at things they find novel or unexpected.

They found the infants applied the rules they had learned of their own language and expected speakers of foreign languages to label objects consistently.

"This finding shows that infants appreciate that words are not shared by speakers of different languages, suggesting that infants have a fairly nuanced understanding of the conventional nature of language," said Henderson.

"People often think that babies absorb language and you don't have to teach them, and they do absorb it and they learn very passively, but they're not just learning willy-nilly," she said.

"They're being smart and making distinctions about the words they hear and use."