Bilingual Babies Learn Grammar Cues In Language By 7 Months

You might think that a baby that grows up in a household where both Japanese and English are spoken would become confused by the clash of tongues. But new research shows that even babies as young as seven months old can pick up on the subtle cues that differentiate the grammatical structures of languages.

University of British Columbia psychologist Janet Werker and Paris Descartes University researcher Judit Gervain tested babies from both monolingual and bilingual homes on their ability to pick up on the rules of languages. Their research was published in a paper appearing Thursday in the journal Nature Communications.

Languages typically fall into two kinds of groups: ones where the word order is verb-object, or VO, or where the word order is object-verb, or OV. Take the English phrase “eat an apple” in English: The verb comes before the object. In Japanese, the equivalent phrase is “ringo-wo taberu” -- directly translated, it’s “apple eat,” with the object coming before the verb.

Babies that grow up in a one-language household learn to comprehend the word order of their native language primarily by picking up on the frequency of articles and prepositions like “the” or “with.” But for babies that are exposed to two languages at once, especially if the two languages rely on opposing word order, they have to use other strategies.

“Bilingual babies can use more surface perceptual cues than monolingual babies,” Werker told reporters during a press briefing at the AAAS Annual Meeting in Boston, Mass.

This sensitivity could partially explain some of the cognitive advantages seen in bilingual children, Werker and Gervain wrote in their paper.

Bilingual infants turned out to be sensitive to both duration and pitch cues in Werker and Gervain’s experiments. Even if they don’t fully understand what words mean, babies seem to be able to tell the difference between articles, prepositions, nouns and verbs based on these sound qualities.

That may be particularly useful in babies trying to acquire two separate languages. In VO languages like English, the primary contrast between words is based on stress -- the more prominent content word is lengthened compared to the article or preposition before it, resulting in familiar iambic patterns. So in a phrase like “to Rome,” the “ro” in Rome is the longest and most stressed syllable.

For OV languages like Japanese, the primary contrast is pitch- or intensity-based. In Japanese, the phrase “Tokyo ni” (“in Tokyo”), the first syllable of “Tokyo” is spoken with a higher pitch and greater intensity.

"The beauty of this work is it shows how exquisite the match is between infant sensitivities and the properties of the worlds' languages," Werker said in an email.

Further research may needed for how monolingual babies exposed to languages with mixed word order, such as Dutch or German, acquire their facility for language. Babies that grow up learning such mixed languages might be sensitive to pitch and duration cues in a similar way to bilingual babies.

“The human language learning system flexibly adapts to the linguistic environment it encounters,” they wrote. "If you speak two languages at home, don't be afraid; it's not a zero-sum game," Werker added in a statement on Thursday.

SOURCE: Gervain et al. “Prosody cues word order in 7-month-old bilingual infants.” Nature Communications published online 14 February 2013.