NEW RESEARCH: Bilingual babies can tell the difference between languages

New Concordia research finds that bilingual infants differentiate between languages as they listen, and they implicitly activate each language to ensure more efficient comprehension.

What’s more, slowing down while switching between languages is common to infants and adults and may be a marker of efficient processing.

Krista Byers-Heinlein, associate professor of psychology in the Faculty of Arts and Science, and PhD candidate Elizabeth Morin-Lessard recently co-authored a study alongside Princeton psychology professor Casey Lew-Williams. It appears in the Proceedings of the National Academy of Sciences of the United States.  

The researchers conducted two sets of audiovisual experiments with 24 bilingual infants up to 20 months old and 24 bilingual adults. Their aim was to determine whether a switch in language affected participants’ ability to match simple spoken words such as “dog” and “book” with their visual equivalents. 

They found that both groups needed more time to process familiar words that were switched in language from the rest of the sentence. They spent less time looking at the labelled object and their pupils widened — a sign of additional neural processing effort.

This difference was reduced or non-existent, however, when the switch was from a non-dominant to a dominant language, or when it occurred after a sentence break.

The findings confirm the hypothesis that bilinguals use a method of language control that can be likened to a double-edged sword: by anticipating words that are likely to come up in conversation, it helps speakers process words in the expected language. But this results in small processing slowdowns when the language is switched.

“We theorized two possibilities for language processing in bilingual infants,” says Byers-Heinlein, the study’s lead author and the mother of a bilingual child.

“One possibility is that the words ‘chien’ and ‘dog’ are basically the same for bilingual infants. The other is that their minds somehow implicitly differentiate between the English and French words. Language is spoken pretty quickly, and if you’re learning that language, you have to process it as it comes.”

As such, she says a good strategy would be to assume that a speaker will most likely continue in the same language rather than switching languages, and hold the words in mind that are likely to come up in sequential speech.

From infancy to adulthood

Previous research on bilingual adults has shown that they implicitly monitor and control the language they are speaking by inhibiting the second language or enhancing the intended one. This causes them to slow down when they must switch to speaking their other language.

The study provides the first experimental evidence of language differentiation in bilingual infants’ representation of words. For instance, the finding that they activate heard languages and are slowed down by language switches would not be possible unless infants were already representing words in separable language systems.

The study also provided surprising results regarding bilingual adults.

“What’s interesting is that the words used were super easy,” says Byers-Heinlein, who is also the Concordia University Research Chair in Bilingualism.

“You see a dog and a book onscreen, and you’re asked to identify one of them. What could be easier? You just look at it. Yet we found that even adults were slowed down a little during switches.”

For Byers-Heinlein, the fact that babies and expert language learners alike share these difficulties is not the sign of a problem, but is rather a powerful indicator of the commonalities of language learning from infancy to adulthood.

“The fact that bilinguals experience small processing slowdowns during language switches is not a bad thing. It means they’re processing language in an efficient way.”

Read the cited study.