"I Want My Child to Be Bilingual": What You Can and Can't Do at Home

Why this topic is on your mind

“I want to raise my child to be bilingual”: for anyone raising children, this is probably a theme you have thought about at least once. In particular, parents who don’t speak English themselves and have struggled with learning English tend to wish strongly that “I don’t want my child to go through the same thing”.

On the other hand, once you start looking into it, the information swings to extremes. From products claiming that “if you play English in the background at home, your child will grow up bilingual” to cold opinions that “in a Japanese environment, however hard you try, a child can’t become bilingual”. The current situation is that it is hard to find a basis for deciding which to believe.

This article aims to set out, as honestly as possible and based on research findings, how far you can really get when aiming for “bilingual” in an all-Japanese family, and beyond what point you can’t. Rather than nice-sounding words, it offers a map for setting realistic goals.

First, define the word “bilingual”

Before starting the discussion, let’s sort out the word “bilingual”, because this one word actually covers very different states.

When English schools and learning materials advertise “your child can become bilingual”, many parents unconsciously picture the “balanced bilingual” at the right end. But in research, this is quite a special state, and reaching it through the home environment alone is not realistic.

On the other hand, up to the “receptive bilingual” at the left end, understanding English when hearing it and feeling familiar with English, is well within reach at home. When you say “make my child bilingual”, which level are you aiming for? Putting this into words is the starting point for a realistic plan.

Research 1: How much English input is needed to grow up bilingual?

Now let’s get into the research. When thinking about bilingual education at home, the issue that is most unavoidable is “the amount of input needed”.

showed a result of decisive importance: for a child to develop vocabulary and grammar steadily in a language, input in that language needs to make up a substantial proportion of waking hours.

Specifically, among the bilingual children in the study, children whose share of English input was low (about 20% or less of the total) tended to show markedly delayed growth in English vocabulary and grammar. On the other hand, in children for whom each language made up 30-40% or more of input, that language developed steadily.

Let’s apply this to an all-Japanese family. If we assume a child is awake for 12 hours, 20-30% of that is 2.4 to 3.6 hours a day. Converted to a week, that is 17 to 25 hours. You can see how thin an exposure a 60-minute English school once a week (= 1 hour a week) is compared with this level.

Research 2: Vocabulary is measured “across both languages combined”

There is another basic study worth knowing when thinking about bilingual education at home.

offered an important perspective on bilingual children’s vocabulary development. The result was that bilingual children appear to have smaller vocabularies than monolingual children when only one language is looked at, but when both languages are counted together, they have the same total vocabulary as monolingual children.

This has two implications.

The first is that if you evaluate a bilingual child only by “the number of English words”, they will always look lower than they really are. Falling short when compared with monolingual children of the same age on English vocabulary is a problem with the evaluation method itself.

The second is a more practical implication: it is thought that there is a rough upper limit to the total vocabulary capacity a child’s brain can process. If you cut time spent on Japanese and shift it to English, English vocabulary increases, but Japanese vocabulary decreases by that much. “Increasing English” in many cases goes together with “decreasing Japanese”.

Research 3: OPOL (one parent, one language) is not a cure-all

When an all-Japanese family tries bilingual education at home, what is often introduced is the OPOL (One Parent, One Language) strategy: the approach of “Dad speaks in English, Mom speaks in Japanese”.

OPOL is a strategy that has long been practiced in families of international marriages and has also attracted attention in research. But looking at decisive large-scale research, the evaluation is a little more cautious.

showed results that partly overturned conventional wisdom about bilingual education at home.

The survey classified parents’ language use patterns at home into several types (both parents only the minority language / one parent the minority language + one parent both languages / OPOL / one parent only the minority language + one parent only the majority language, etc.). It found results showing that it cannot be said that “with OPOL, children automatically become bilingual”.

For example, in the pattern where both parents speak the minority language (= the English side) at home, the probability of children speaking the minority language was very high. On the other hand, with OPOL (only one parent speaking the minority language), the probability of children actually coming to speak the minority language stayed moderate. It was further shown that when only one parent speaks the minority language and the other parent speaks only the majority language, the risk of children not speaking the minority language increases.

Reading this research in terms of an all-Japanese family reveals an even harsher reality. In a family where neither parent is a native English speaker and the family lives in Japanese society, there is hardly anyone, either at home or in society, “you can’t communicate with unless you use English”. Structurally, the child’s motivation to recognize English as “a language I need to use” becomes weak.

Research 4: The first language is the very foundation for a second language

Since the discussion so far has run in the direction of “bilingualism at home is difficult”, let’s finally introduce one more important line of research from a different angle.

presents an important perspective on the relationship between the first language (mother tongue) and the second language.

One of Cummins’s central claims is that cognitive and linguistic abilities well developed in the first language (mother tongue) can also be put to use in acquiring a second language (the interdependence hypothesis). In other words, a child who has well developed the ability to “think”, “explain”, “tell stories”, and “handle abstract concepts” in Japanese can “build” that ability onto English when they learn English later.

Conversely, there is a risk that if you devote time to a second language while the cognitive and academic foundation of the first language has not developed, both languages end up half-developed. This is also called “semilingualism”, and it has been pointed out that in the long run it can actually be negative for school performance and thinking ability.

BICS and CALP: two different kinds of language ability

Cummins also thought of language ability as divided into two: BICS and CALP.

• BICS (Basic Interpersonal Communicative Skills): language ability at the level of everyday conversation. Communication that works with the help of context, such as greetings, shopping, and small talk.
• CALP (Cognitive Academic Language Proficiency): cognitively advanced language ability needed for school subjects and abstract discussion. Abilities such as making sense of textbooks, explaining one’s thinking logically, and understanding complex stories.

When you feel that “my child has become able to speak English” through an English school or learning at home, it is almost entirely in the domain of BICS. Developing CALP requires far longer time and systematic learning in that language (= learning school subjects). From the research findings, it is realistic to think that what an all-Japanese family can reach through learning at home alone is, at most, around the entrance to BICS.

“What you can do at home” and “what is realistically difficult”: an honest sorting

Based on the research so far, here are realistic expectations when an all-Japanese family tries bilingual education at home.

Calmly accepting “what is realistically difficult” is by no means giving up. Rather, it is healthy preparation to avoid setting unreachable goals and continually putting pressure on both your child and yourself.

There are situations where it is better that the parent’s English is limited

A question often debated in all-Japanese families is “should parents speak to their child in broken English?”

On this, research cannot say across the board that “you should”. There are two reasons.

First, as De Houwer (2007) showed, even if one parent speaks English that does not function at home as “a language that needs to be used”, the effect in getting the child to actually use English is limited, because the child does not perceive that “with Mom, I won’t be understood unless I speak English”.

Second, it has been pointed out that long exposure to English with unnatural pronunciation or grammar may distort the child’s sound image and grammatical image of English. This cannot be said definitively, but it is an issue to consider as a risk.

For this reason, in families where both parents are non-native speakers, rather than straining to “speak to the child in English yourself”, it is more consistent with research findings to build native audio (picture book CDs, English songs, cartoons) into daily life, while the parents continue warm exchanges in Japanese.

Designing “realistic contact with English” at home

So what can an all-Japanese family actually do? Within a range that does not contradict research, here is a realistic design.

Ages 0-2: centered on sounds and songs

The goal at this age is getting familiar with the rhythm and intonation of English sounds. It is not a time to expect perfect pronunciation or memorization of vocabulary.

• Play English nursery songs (Mother Goose, nursery rhymes) gently as background music in daily life
• Read English picture books (short ones with rhythm and repetition) alongside Japanese picture books (even if you can’t read them, a CD recording is enough)
• If singing in English is a burden for the parent, just playing a recording and swaying together is enough

Ages 2-4: link it to fun time

A time when vocabulary and expressions start to increase. The goal becomes creating the link “English = fun time”.

• Short English cartoons (Sesame Street, Peppa Pig, etc.) as time to enjoy together with a parent
• Create “favorite” English picture books (reading the same book over and over works better for retention)
• If your child goes to an English school once a week, frame it positively as “the day I get to see English and my fun teacher and friends” (see also the sister article “How should you choose an English conversation school?”)

Ages 4-6: nurture conversation and interests

A time when children begin to be interested in abstract concepts. Rather than English itself, you can use content they can encounter in English (the child’s areas of interest, such as animals, space, and vehicles) as the entry point.

• Choose English picture books and videos on themes your child is interested in
• Don’t make “being able to do English” the goal; build up experiences of “meeting things I like in English”
• This is also a time when reading and writing in Japanese grow, so prioritize not sacrificing reading time in Japanese

Closing dialogue

If you also read the sister articles Does early English education really work? and How should you choose an English conversation school?, I think it will be easier to set your own criteria from three angles: “when and how to start”, “how to choose”, and “what you can do at home”.