Raising a Bilingual Child: Myths and Evidence

A bilingual child, in the sense researchers use, is simply a child who hears and uses two languages regularly. It does not mean equal fluency in both, and it rarely does: most bilingual children have a stronger language that shifts with school, friends and who they spend time with. Parents raising a child this way get plenty of advice, and much of it is out of date. Here are seven common beliefs, and what the research actually supports.

Myth: Two languages cause a speech or language delay

They do not. The American Speech-Language-Hearing Association (ASHA) states plainly that learning two languages does not cause language disorders or delays. Bilingual children reach the major milestones, babbling, first words around the first birthday, and early word combinations in the second year, within the same age ranges as monolingual children.

The confusion comes from vocabulary counts. A bilingual toddler may know fewer words in each language than a monolingual peer, because some words are known only in one language (kitchen words at home, playground words in English, for example). When researchers count the words a child knows across both languages, an approach used in studies by Barbara Zurer Pearson, Sylvia Fernández and D. Kimbrough Oller in the 1990s, bilingual children's total vocabulary is broadly comparable.

The practical consequence matters. A bilingual child can still have a genuine language disorder, at about the same rate as any other child, and that should not be dismissed as "just the two languages". ASHA advises that a speech-language pathologist assess a bilingual child in both languages. If a child is not saying any words in either language by about 15 to 18 months, raise it with the pediatrician.

Myth: Mixing languages means the child is confused

Switching between languages within a conversation, or even within a sentence, is called code-switching, and it is normal. Bilingual adults do it all the time, and studies of children show their mixing follows patterns: they tend to borrow a word from the other language when they do not know it yet, or when it fits better, and they adjust how much they mix depending on who they are talking to. Fred Genesee at McGill University and others found that even toddlers can tell the two languages apart. A child who says a Spanish sentence with one English noun in it is filling a gap, not losing track.

Myth: You have to follow one parent, one language

One parent, one language (often shortened to OPOL) is a well-known approach in which each parent consistently speaks a different language to the child. It works for many families. It is not required, and it is not the only route.

Annick De Houwer, who surveyed around 2,000 bilingual families in Belgium, published findings in 2007 showing that the arrangement most strongly linked to children actually speaking the minority language was both parents using it at home. Families following OPOL had more mixed results. Other workable setups include speaking the home language inside the house and the community language outside, or setting aside particular times or activities for each. What seems to matter most is that the child hears the language a lot, from people who need them to answer in it.

Myth: After a certain age it is too late

Starting early has real advantages, particularly for accent. Children who begin a language young are more likely to sound like native speakers. A large online study by Joshua Hartshorne, Joshua Tenenbaum and Steven Pinker, published in Cognition in 2018 with data from about 670,000 people, suggested that the ability to learn grammar stays strong until late adolescence and then declines, and that reaching native-like grammar is most likely for people who start by around age 10. That study's methods have been debated.

None of this means a five-year-old or a twelve-year-old cannot become a capable speaker. It means the outcome may look different. People learn languages successfully at every age.

Myth: Bilingual children are smarter

This is the claim most often used to sell bilingualism, and the evidence is less settled than it sounds. Psychologist Ellen Bialystok and colleagues reported in a series of studies that bilingual children and adults performed better on some tasks involving attention control and switching between rules. Later, larger studies often failed to replicate those differences. A 2015 paper by Angela de Bruin and colleagues in Psychological Science found that studies reporting an advantage were more likely to be published than those that did not, and a 2018 meta-analysis by Minna Lehtonen and colleagues in Psychological Bulletin found no reliable advantage once that bias was accounted for.

The fair summary is that any cognitive edge is small, inconsistent or absent. There are plenty of better reasons to raise a bilingual child: talking with grandparents, belonging to a community, reading its literature, and a skill that is genuinely useful.

Myth: A video or app can do the work

Babies learn language from people. In a well-known 2003 study in the Proceedings of the National Academy of Sciences, Patricia Kuhl and colleagues found that American nine-month-olds who spent short sessions with a live Mandarin speaker kept their ability to hear certain Mandarin sounds, while infants who got the same material by video or audio recording did not. Media can add vocabulary for older children. It does not replace conversation.

Myth: Drop the home language once school starts

Families are sometimes told to switch to the school language at home so the child catches up faster. This advice carries a real risk: the home language is lost. Lily Wong Fillmore's research in the early 1990s found that many young children of immigrant families in the US shifted toward English after starting preschool, and that the home language often weakened quickly once that happened.

Losing it can cut a child off from grandparents and extended family. Strong skills in the first language also tend to support learning to read in the second, a link Jim Cummins described as linguistic interdependence. If school pulls hard toward one language, give the other one a regular, protected place, such as a weekly call with a grandparent in which only the home language is used, and keep books in that language on the shelf at home.