Children who experience two languages from birth typically become native speakers of both, while adults often struggle with second language learning and rarely attain native-like fluency. With roughly two thirds of the world’s population estimated to understand or speak at least two languages, bilingualism has become the norm rather than the exception in many parts of the world.
Although some might be concerned that bilingualism puts children at risk for language delay or academic failure, research does not support this. To the contrary, studies consistently show that, besides the obvious practical and economic gains, bilingualism leads to a number of cognitive advantages. Emerging research supports the view that the capacity to learn language can be equally applied to two languages as to one.
A recent study conducted by the University of Washington (Institute for Learning and Brain Sciences) compares the major milestones in bilingual and monolingual language acquisition, outlines the reasons behind the frequently observed variability in bilingual language learning, and describes the cognitive benefits of bilingualism. Here are the main outcomes.
1- Language learning in the first year of life
Until about 6 months of age, infants are capable of hearing the differences between the consonants and vowels that make up words universally across all languages. By 12 months of age, discrimination of sounds from the infant’s native language significantly improves, while discrimination of non-native sounds declines (Kuhl et al., 2006). Infants’ initial universal ability becomes more language specific, like that of an adult, by 12 months of age.
Research shows that the infant brain is more than capable of learning two languages simultaneously. Young children learn language rapidly; however, the quality and quantity of language they hear plays a key role in the learning process. One study shows that infants exposed to a new language at 9 months of age in play sessions by a live tutor learn in just 6 hours to discriminate foreign language sounds at levels equivalent to infants exposed to that language from birth. However, no learning occurs if the same material on the same schedule is presented via video or audiotapes (Kuhl, Tsao, & Liu, 2003). Thus, early language learning is critically dependent on social interactions, and on the quality of speech that children hear.
Taken together, in monolingual and bilingual children alike, language growth reflects the quality and quantity of speech that infants hear. Young infants learn best through frequent, high-quality, social interactions with native speakers.
2- Vocabulary and grammatical development
Young children exposed to two languages from birth typically begin producing their first syllables and their first words at the same age as children exposed to a single language. Furthermore, the bilingual course of vocabulary and grammatical growth looks very much like the trajectory followed by monolingual children; the kinds of words children learn, and the relationship between vocabulary and grammatical growth in each language replicate the monolingual pattern.
Nevertheless, the effect of bilingual experience on language production and comprehension is often reported as a lag in vocabulary and grammatical acquisition. Although some studies have shown that bilingual children are within monolingual norms for the age at which they achieve basic vocabulary and grammatical milestones of language development, several studies report that bilinguals control a smaller vocabulary in each language than monolinguals, and lag behind on grammatical measures when skills are measured on a single language (Hoff et al., 2012). Given the extensive research showing that children’s language skills reflect the quantity of language that they hear, these findings are not surprising. Bilinguals split their time between two languages, and thus, on average, hear less of each language. Importantly, however, studies consistently show that bilingual children do not lag behind monolingual peers when both languages are considered. For example, bilingual vocabulary sizes, when combined across both languages, are equal to or greater than those of monolingual children. Similar findings are reported on measures of grammatical knowledge.
3-Learning to read
Reading is a complex process acquired through explicit training, typically after a child has learned to speak in full sentences. Studies with monolingual children demonstrate the critical role of oral language in reading and academic success. Thousands of U.S. children find themselves in situations where they must acquire the fundamentals of reading in a language that they do not speak, or where their linguistic knowledge is extremely poor. Not surprisingly, studies often report that bilingual immigrant children perform worse than monolingual English children in reading acquisition. However, research demonstrates that exposure to two languages increases phonological awareness, which is the ability to recognize and manipulate the sound units of language and is one of the best predictors of reading ability.
4-Cognitive benefits of bilingualism
Contrary to the once held concern that bilingualism causes confusion, research shows that simultaneous exposure to two languages is related to several cognitive benefits. Part of the concern about confusion arises due to “code mixing” or “code switching.”
Bilingual children occasionally combine words or phrases of both languages when interacting with their peers, parents of teachers. It is important to understand that code switching is natural for bilingual adults and children and reflects the fact that bilinguals often know certain words better in one language than in the other. Code switching in bilingual adults and children is rule governed, not haphazard, and bilingual children follow the same principles as bilingual adults (Paradis, Nicoladis, & Genesee, 2000).
Rather than causing confusion, it is now understood that the constant need to manage attention between two languages fosters children’s thinking about language per se, and leads to increased metacognitive and metalinguistic skills (Bialystok, 2007). Bilingual infants as young as 7 and 12 months have been shown to be more flexible learners of language patterns compared to monolingual infants (Kovacs & Mehler, 2009). Bilingual toddlers exhibit a prolonged period of flexibility in their interpretation of potential words (Graf Estes & Hay, 2015), and bilingual 2- and 3-year-olds are more flexible learners of additional labels for previously known actions or objects, whereas monolingual children often find it difficult to learn labels for actions or objects that already have a name (Yoshida, 2008).
A growing body of evidence also suggests that bilinguals exhibit enhancements in executive functioning, which have been observed in children, young adults and middleaged and older adults (Bialystok, Craik, & Luk, 2012). The primary processes of the executive functioning systems are switching attention, flexible thinking (cognitive flexibility), and updating information in working memory. Bilingualism requires the constant managing of attention to the target language. Research suggests that experience with two languages enhances the relevant brain networks, making them more robust for executive functioning throughout the lifespan. Interestingly, the accumulating effect of dual language experience translates into protective effects against cognitive decline with aging and the onset of Alzheimer’s disease (Craik, Bialystok, & Freedman, 2010). Recent brain studies indicate that differences between monolinguals and bilinguals in executive functioning are present at an early age (Ferjan Ramírez et al., 2016), and persist throughout the school years (Arredondo et al., 2016) and into adulthood (Abutalebi et al., 2011; Stocco & Prat, 2014).
A growing body of research indicates that the experience of bilingualism alters not only the scope of language acquisition and use, but also a broader scope of cognitive processing from a very young age onward. Bilingual children perform equally well or better than monolinguals when both languages are considered. Studies suggest that optimal learning is achieved when children start learning two languages at an early age (i.e. between birth and 3 years of age) through high-quality interactions with live human beings, and both languages are supported throughout the toddler, preschool, and school years. Supportive environments for bilingual learning encourage parents and caregivers to use the language in which they are most fluent and comfortable, value both languages equally, and view bilingualism as an asset that brings about important cognitive, social, and economic benefits.