Bilingual Infants Develop Early Language Differently Than Do Monolingual Infants

New research conducted at the Universities of British Columbia and Ottawa, Canada, shed new light on language development in infants in a study designed to compare speech-sound learning in monolingual children to speech-sound learning in bilingual children.

The field of sociolinguistics is influencing world-wide ideas about the efficacy and appropriateness of governmental language policy and language education that is adverse to bi- and multilingualism. Due to increasing immigration, variations in official language policies, and changing cultural norms, many more infants in Western countries are now being raised bilingually.

In the past, nearly all experimental work in infant language development has focused on monolingual infants. As a result, relatively little is known about acquiring two languages from birth.

The researchers in the field of child development sought to determine whether the demands of acquiring more sounds and words (speech-sound variation and bi-lingual replication of object labels) lead to differences in language learning and development. An important part of language development is the ability to pay attention to native speech sounds which differentiate and guide word learning.

For example, monolingual English learners expect that the nonsense words "bih" and "dih" refer to different concepts because "b" and "d" are different consonant categories in English: they are different phonemes signifying different units of meaning. By 17 months of age, monolingual English infants use native-language speech-sound (phonemic) differences to guide them as they learn words, i.e., differentiate meaning within minimal sets of words (pan, can, man, ban; hit, hip, him, his, hill). Do bilingual infants show a similar developmental pattern in regards to age of speech-sound differentiation?

The study found that Infants who are raised in bilingual homes learned two similar-sounding words in a laboratory task at a later age than infants who are raised in monolingual homes. This difference in age of learning discrimination of speech-sound learning, which is thought to be advantageous for bilingual infants, appears to be due to the fact that bilingual babies need to devote their attention to learning the general associations between words and objects--usually an object has a word label in each language--for a longer period, whereas monolingual children can begin to focus attention on specific detailed speech-sound information.

This finding suggests an important difference in the mechanics of how monolingual and bilingual babies learn language.

The study revealed that bilingual infants follow a slightly different pattern than monolingual infants. Researchers tested bilingual children ages 14, 17, and 20 months on their ability to associate two words that differed in a single consonant sound with two different objects: Researchers used monolingual minimal set information raising the query: So what do bilingual infants do with monolingual minimal set information? Earlier research has found that monolingual infants differentiate single consonant sounds with two different objects at 17 months of age.

Experiment 1 included a heterogeneous sample of bilingual babies, i.e., those exposed to English and any other language. Experiment 2 tested two homogeneous groups of bilingual infants, i.e., English-French and English-Chinese.

In both experiments, bilingual infants were repeatedly presented with a crown-shaped object that was called "bih" and a molecule-shaped object called "dih," which is a presentation of monolingual information as opposed to bilingual information. They were then tested on their ability to notice a switch in an object's name, e.g. the molecule-shaped object being called "bih" instead of its proper name "dih." In all of the bilingual groups, the infants failed to notice the minimal sound (phoneme) change in the object's name until 20 months of age.

The researchers suggest that this later development in bilingual infants of recognizing and using discrete speech sounds--individual phonemes, such as consonants--to direct word learning is due to the increased demands of learning two languages; in other words, of separating two discrete sound systems each with individual phonemic units of meaning. Ignoring the consonant detail in a new word may be an adaptive tool used by bilingual infants in learning new words within appropriate language systems.

The studies show that by paying less attention to the detailed sound information in the word, bilingual infants can devote more cognitive resources to making the links between words and objects within discrete language systems. Researchers theorize that outside the laboratory, there is little cost to overlooking some of the consonant detail in new words, as there are few similar-sounding words in infants' early vocabularies.

Extending this phoneme differentiation aspect of word learning for a few months longer than monolinguals do may help bilinguals "keep up" with their peers in terms of age of first speech and vocabulary size. Indeed, previous research has shown that bilinguals and monolinguals achieve language-learning milestones (such as speaking their first word) at similar ages and have vocabularies of similar sizes when words from both languages are taken into account in calculating bilingual vocabulary size.

"Through studies with bilingual infants, we can gain a deeper understanding of language development in all infants," according to Christopher T. Fennell, assistant professor of psychology at the University of Ottawa and the lead author of the study. "In addition, the findings emerging from such studies will have practical implications for parents who are raising their children in a bilingual environment by revealing how young bilinguals acquire language."

The report appears in the September/October 2007 issue of the journal Child Development/Society for Research in Child Development.

"Babies raised in bilingual homes learn new words differently than infants learning one language," University of British Columbia; University of Ottawa, Canada; Society for Research in Child Development.