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(Daria Kiseleva / The McGill Tribune)

Bilingual infants take a unique path to speech development

Science & Technology by

Newborn babies have many monumental tasks before them, a key one being the acquisition of language. In our first few years, we must learn to recognize characteristic sounds, distinguish separate words, interpret more complex word combinations, and eventually assign meaning to what we hear. For infants raised in bilingual environments, speech perception develops in a slightly different manner than for their monolingual peers.

Professor Dr. Linda Polka of McGill’s School of Communication Sciences and Disorders researches “crib bilinguals”—individuals who were taught two languages since infancy. According to Polka, crib bilinguals develop a “hybrid” perceptual system with unique capabilities as opposed to independent systems for each language.

A study co-authored by Polka tested the ability of infants to discern the subtle difference between the French /d/ and English /d/ sounds. Surprisingly, bilingual infants were able to perceive the nuance, while by a certain age monolingual francophone infants could no longer recognize the distinction.

“There’s an extra thing that comes out of combining the languages together, a difference they can access that monolinguals can’t access,” Polka said.

Although bilingual language acquisition comes with an increased cognitive demand, bilingual individuals benefit from many cognitive advantages, including better focusmultitasking, and problem solving skills.

However, simultaneously learning two languages in infancy may also present unique challenges. For example, word segmentation is a key skill in language acquisition. Word segmentation refers to breaking down continuous sounds into words. Acquiring a sense for a natural rhythm of the language facilitates word segmentation, but the task becomes more complex when the two languages have different rhythms.

English is considered a “stress-timed” language as it is characterized by a fairly constant time interval between stressed syllables. Specifically, most English nouns have a stress on the first syllable.

French, on the other hand, is a “syllable-timed” language where every syllable has an approximately constant duration.

Consequently, the strategy used to segment multisyllabic words in one of those languages will not work in the other.

“Typically, babies learning both of those languages seem to be easily confused by [their different rhythms],” Polka said.

Polka’s more recent research looked at how French-English bilingual babies perform at word segmentation compared to their monolingual peers. In the experiment, infants listened to a story which featured a word multiple times and then heard that word in isolation. If a baby recognized the word, it meant that they could successfully segment it from the continuous stream of speech. The procedure was performed once in French and once in English.

At the age of eight months, monolingual francophone and anglophone infants could segment two syllable words exclusively in their native language. However, bilingual infants were only able to segment in French, and only if French was tested first.

“Something is making [word segmentation] harder for the bilingual babies,” Polka said. “Part of what they have to do is figure out which [of the two languages] they are hearing.”

Consequently, the experiment was adjusted to give the bilingual infants more time to listen to the story. With this additional help, the babies were able to segment both English and French speech in any order.  

Polka hypothesizes that tracking syllables might be the go-to strategy when infants don’t know which language they are hearing, since syllable patterns are more universal across languages than stress patterns. As a result, syllable-timed French speech could be segmented when it was heard first, but listening to English first for an insufficient period of time simply caused confusion.

According to the Dana Foundation, more than half of the world’s population today is bilingual or multilingual. While the vast majority of research on language acquisition has traditionally focused exclusively on monolingual learners, future studies into its bilingual mechanisms promise to provide more insight into the experience of many.

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