With the United States becoming increasingly diverse, and school districts beginning to make accommodations that promote bilingualism, one of the most pressing questions that our schools face is whether bilingual education is worth the additional investment of time and resources. If bilingual children need to develop two lexical repertoires and monolingual children need to develop one, does that mean bilinguals require double the amount of time to learn vocabulary? After all, they have twice the number of words to learn.
To address this, let's first establish how children learn new words through defining vocabulary breadth and depth. Vocabulary breadth refers to the number of words that children know. By the age of 3-4 years old, children generally understand 1,000-2,000 words, and are able to express about 800-1,500 of them. By the end of high school, this number increases to approximately 40,000 to 50,000 words. Vocabulary depth refers to how well a child understands a word, which includes the sound and spelling of the word (phonics), how the word can be broken apart (morphology), when and how to use it (pragmatics), and what meanings the word might have (semantics). With all these dimensions to learning a single vocabulary word, do bilingual children need more time and resources to learn two linguistic systems? The answer is it depends on how you look at it.
On one hand, researchers have shown that the rate of vocabulary acquisition is similar in both monolingual and bilingual speaking children. To understand how this works, we need to think about the context in which vocabulary is learned. For example, a child who speaks Chinese at home may learn about 1,000 house-vocabulary, food-vocabulary, and family-vocabulary words in Mandarin. Then at preschool, she learns about 1,000 classroom-vocabulary, subject-vocabulary, and playtime-vocabulary words in English. Meanwhile, a monolingual speaker learns all home and preschool vocabulary words in English. While both children learn vocabulary at a similar rate, acquiring approximately 2,000 words before entering elementary school, these 2,000 words may be pieced together from different languages for the bilingual learner, according to the context in which each word was learned.
On the other hand, vocabulary can take more time to develop in bilingual children if they are not given the resources needed to nurture bilingual growth. Entering school, bilingual children (i.e. English Language Learners) are tested for language proficiency, usually in the dominant language, English. When these children are unable to produce vocabulary words in English, we often assume that they have no concept of what the vocabulary words might mean. The reality is they probably do, but just not in English. Children identified as ELLs are given remedial help and play catch up by assigning English words to concepts they already know. Meanwhile, their monolingual schoolmates are learning new words and new concepts in mainstream classes at a much faster rate than bilingual learners.
Research shows that when bilingual children are provided optimal environments for learning both languages, they are able to develop sizable and deep vocabularies in both languages. In order to know what these optimal environments should be, it is critical for schools to perform accurate - and possibly bilingual - assessments of what children know when they enter school. Using this information, schools can create individualized language plans that address the specific gaps of knowledge in both lexical repertoires. Without this crucial intermediation, children's vocabulary growth becomes vulnerable and stunted, which grossly affects the trajectory of their first and second language development.
As America becomes increasingly diverse, and school districts take steps to prioritize bilingual education, challenges will continue to arise as we consider the linguistic support needed in this transition from home to school. Still, if children have the potential to learn two languages just as well as one language, how might that impact this next generation as they engage in our globalized economy?