If you move to another country where your language is not spoken, the age of your child when they start learning the language has an effect on their proficiency.
When a child learns one language first and another one later, this is called Sequential or Successive Acquisition. Parents want to know if children arriving in a new country, where a new foreign language is spoken, will end up speaking the language proficiently or even attain a native speaker level.
The consensus among researchers is that the younger the child is when they arrive, the better. The ‘Critical Period’ Hypothesis says that moving to the country before puberty (so a maximum of eleven or twelve years old) is optimal if you want the child to acquire a native speaker grammar level, but not necessarily the accent.
Other research suggests that from the age of eight, our ability to learn languages becomes “slower and more academic.” After that age, even with high exposure, living in the target country and going to school there, the child will never gain that native intuition that a sentence is right or wrong.
However, this does not mean that children arriving as teens cannot acquire a native grammar level and speak with a native accent. There are other factors, such as aptitude and natural ability, which are hard to predict and study; but these factors have a strong influence in determining a child’s final language proficiency.
So, the general consensus is that the younger children are when they begin to learn a language, and the more exposure they get, the better they will become. Lightbown and Spada (see bibliography), for instance, state that the basics of the language have been acquired by around the ages of five or six years old and are developed as the child becomes older.
So bilingual families, according to this view, should aim for high linguistic interaction and exposure in those earliest years. This also means that strengthening the heritage language at home first is not a problem, as children will learn the local language to a native level when they go to preschool.
So, how much exposure to the heritage language do they need per week to become bilingual?
This is the million-dollar question! Remember we are talking about learning the heritage language at the same time as the local language. Let us take the first five years, as they seem to be crucial.
It has been estimated that by the age of five, monolingual children, living in the dominant language environment, who are awake ten to twelve hours a day, may have been exposed to around 20,000 hours of language from parents, siblings, friends and media input (so, it’s not all interactive). This may not be a totally accurate, but it shows that high exposure in the early years is essential.
Looking back at what I did with my son in the first five years, I aimed for two or three hours interactive contact from Monday to Friday and a minimum of six hours interactive input on holidays and weekend days, playing games, sports, taking walks, going on outings, etc., which included additional hours watching television or films with him (and not just in silence).
He also received passive TV and video input in English when I was not there, sometimes four or five hours. So, he probably had a total of between six and eight hours’ exposure a day, including the (mostly passive) input at the trilingual school of about two hours or more between the ages of three and five. We only spent two or three weeks per year in the UK at that stage.
If five hours seems a lot of media time, remember that just three sessions of two hours per day makes six hours; and you know how quickly time goes when you are binging on Netflix! This was enough for Marc to reach a bilingual native level in English and speak with an English accent.
If you do the maths, and calculate six hours a day from both interactive and passive contact from a bilingual parent, that makes nearly 11,000 hours of input in five years, which is quite a lot less than a monolingual child would get (in theory). However, this seems to more than enough for many children to reach a bilingual native level in the heritage language.
You occasionally meet children who have received fewer hours input and have a higher level of language proficiency than others with a much richer language environment. I’ve heard non-native English speakers with near perfect accents through but massive input from YouTube videos; so this is some evidence that comprehensible and appropriate content through media can be very beneficial.
The main point is that it is best to provide as much language input as you possibly can, especially in those first five to six years.
For more detailed information and advice, check out the book on Amazon: The 5 Key Strategies of Successful Bilingual Families.