Babies as young as 7 months can begin to learn two languages even if they have vastly different grammatical structures, Canadian and French researchers say.

A study by the University of British Columbia and Universite Paris Descartes reports infants in bilingual environments use pitch and duration cues to discriminate between languages, such as English and Japanese, even though those languages use opposite word orders.

In English, a function word comes before a content word -- the dog, his hat, with friends -- and the duration of the content word is longer, while in Japanese the order is reversed, and the pitch of the content word higher.

"By as early as 7 months, babies are sensitive to these differences and use these as cues to tell the languages apart," co-author Janet Werker, a UBC psychologist, said.

Babies also use frequency of words in speech to discern their significance, the researchers said.

"For example, in English the words 'the' and 'with' come up a lot more frequently than other words -- they're essentially learning by counting," Judit Gervain of the Paris university said. "But babies growing up bilingual need more than that, so they develop new strategies that monolingual babies don't necessarily need to use."

"If you speak two languages at home, don't be afraid. It's not a zero-sum game," Werker said. "Your baby is very equipped to keep these languages separate and they do so in remarkable ways."