Research has shown that, contrary to what many people once believed, bilingualism does not trigger confusion, has no inherent negative impact on children’s development and even has some socio-cognitive advantages. In particular, bilingual children show some advantages in understanding the beliefs of others and the communication needs of their conversational partners, picking out the important variables to solve a problem and entertaining two possible interpretations of the same stimulus at once. As well, they achieve higher scores than monolingual children on a number of cognitive ability tests, including mental flexibility, non-verbal problem-solving tasks, understanding the conventional origin of names, distinguishing between semantic similarity and phonetic similarity and the capacity to judge the grammaticality of sentences.
The context in which the bilingualism or second-language learning occurs is important, however. Variables that can affect the outcomes of bilingual development include parental attitudes toward bilingualism, the status of the language(s) in the community and the socio-cultural context in which the children grow up.
Second-language learners take a long time to develop their second-language oral proficiency. Even after five to six years of attending school in the second-language environment, children may not speak as fluently in the language as their monolingual peers. Parents and educators should also be aware that in the early stages of the acquisition of a second language, children who learn two languages may show some developmental lags relative to children who speak only one. However, these lags are typically small and do not last for long periods of time. In terms of general language proficiency, bilingual children tend to have a smaller vocabulary in each language than monolingual children in their language. Nonetheless, their understanding of linguistic structure is at least as good and often better than that of comparable monolinguals.
Children learning to read in two languages that share a writing system (e.g. English and French) show accelerated progress in learning to read; children whose two languages are written in different systems (e.g. English and Chinese) show no special advantage, but neither do they demonstrate any deficit. However, the benefit of learning to read in two languages requires that children be bilingual and not second-language learners whose competence in one of the languages is weak (as a result of a lower degree of involvement in the second language).
Research shows that it is possible to diagnose reading disability in second-language children rather early. In fact, delaying diagnosis and treatment of potential reading disability in second-language children is costly and has long-term consequences for children who have difficulties in learning to read and write in the school language. The profiles of at-risk readers include persistent and extremely poor performance on word recognition, pseudo-word decoding (units of speech or text that look and sound like words in a particular language but that are not actually words) and spelling tasks and concomitant poor performance on phonological processing measures (such as phonological awareness and rapid naming).
Phonological awareness (the ability to break words into their components, synthesize their sounds and learn their features), rapid naming and to some extent verbal working memory are sources of individual differences that are associated with reading development and reading difficulties in monolingual children. These processing skills measured in monolingual and second-language children often correlate with each other, and can predict decoding and spelling skills in both languages. This has been found across different language groups. As well, regardless of the type of orthographies (regularity of correspondence between letters or letter combinations and their associated sounds) involved, second-language learners who have decoding and spelling problems in their first language have difficulties in their second language as well. Finally, second-language learners who have serious problems with word-based reading skills and with the cognitive processes that are necessary to develop good word-based skills in the second language also have poor reading fluency, reading comprehension and writing skills.