Long before they can understand what is being said to them, babies can make strategic use of the sound cues that they hear to distinguish between two languages, a new study has revealed. The finding suggests that children growing up in a multilingual environment are neither confused nor disadvantaged by having to cope with two mother tongues, even when the grammatical structures of the two languages are substantially different from one another.
"Babies are just remarkably prepared to learn about the world around them, and specifically prepared to learn about language," says Janet Werker, a psychologist at the University of British Columbia who co-authored the study, published in the journal Nature Communications.
Scientists have long been intrigued by the question of exactly how babies manage to learn more than one language at a time. The feat is all the more remarkable because, from a baby's perspective, "it's not immediately obvious that there are two languages mixed together in the input," says Krista Byers-Heinlein, an assistant professor of psychology at Concordia University in Montreal.
Previous research has shown that short, frequently occurring words like "a" and "the" play a role in helping a baby discern spoken language. But word frequency alone can't allow a baby to distinguish between two separate languages since short words may occur at a similar rate but fall in different places when the grammar changes.
Werker and her collaborator, Prof. Judit Gervain of the Université Paris Descartes, France, set out to test if bilingual babies can get additional help from the underlying sound patterns in a language. The experiment involved 71 babies at seven-to-eight months of age. One third of the group were from bilingual families where the two spoken languages obey different grammatical rules, such English and Japanese. In that case, English grammar follows a subject-verb-object order (as in "'The boy ate the apple") while Japanese is subject-object-verb.
In Werker's lab, babies from bilingual and unilingual families were tested first by having them listen to a made-up language in which the words have no meaning, but their changing pitch or duration resemble the sing song style of a real human tongue. Shorter duration on highly frequent words universally signals a subject-verb-object word order, whereas lower pitch on highly frequent words signals subject-object-verb.
Then the sing-song cues were removed to determine what the babies had learned. The babies from bilingual families learned an order corresponding to subject-verb-object if they had first heard duration differences, and subject-object-verb if they had first heard pitch differences. I contrast, those babies who were growing up monolingual could not use the sing-song cues to learn two different word orders. The results indicate that the bilingual babies were apparently adept at using sound cues like pitch and duration to identify which grammatical version of the fake language they were hearing in the first place.
Dr. Werker says the results demonstrate that preverbal children are already attuned to a variety of patterns and clues that can help them navigate a multilingual situation. "It's like a sudoko puzzle," she says. "There are different sources of information that help babies pull out whatever they need to get on with whatever language or languages they need."
Fred Genesee, a professor of psychology at McGill University who was not involved in the study says it helps illuminate how children who grow up in a multilingual household already seem to have an intuitive grasp of two distinct languages and can switch between them appropriately even as they are just beginning to utter their first words.
"There's clearly a lot going on in the silent period before they start speaking," says Prof. Genesee.
He adds that the work should help dispel concerns that children in multilingual settings are overburdened by language overload. Rather, he says, "There's a sense that monolinguals are underusing their linguistic capacity."
Dr. Werker will present her findings on Friday at the annual meeting of the American Association for the Advancement of Science in Boston.
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