It is often thought that it is better to start learning a second language at a young age. But research shows that this is not necessarily true.
In fact, the best age to start learning a second language can vary significantly, depending on how the language is being learnt.
The belief that younger children are better language learners is based on the observation that children learn to speak their first language with remarkable skill at a very early age.
Before they can add two small numbers or tie their own shoelaces, most children develop a fluency in their first language that is the envy of adult language learners.
WHY YOUNGER MAY NOT ALWAYS BE BETTER
Two theories from the 1960s continue to have a significant influence on accounting for this phenomenon.
The theory of "universal grammar" proposes that children are born with an instinctive knowledge of the language rules common to all humans. Upon exposure to a specific language, such as English or Arabic, children simply fill in the details around those rules, making the process of learning a language fast and effective.
The other theory, known as the "critical period hypothesis", posits that at around the age of puberty, most people lose access to the mechanism that made them such effective language learners as kids.
These theories have been contested but continue to be influential.
Despite what these theories suggest, however, research into language learning outcomes demonstrates that younger may not always be better.
In some language learning and teaching contexts, older learners can be more successful than younger children.
It all depends on how the language is being learnt.
LANGUAGE IMMERSION ENVIRONMENT BEST FOR KIDS
Living, learning and playing in a second language environment on a regular basis is an ideal learning context for young children.
Research clearly shows that they are able to become fluent in more than one language at the same time, provided there is sufficient engagement with rich input in each language. In this context, it is better to start as young as possible.
TEACHER INPUT IDEAL IN LATTER YEARS OF PRIMARY SCHOOL
Learning in language classes at school is an entirely different context. The normal pattern of these classes is to have one or more hourly lessons per week.
To succeed at learning with such little exposure to rich language input requires metacognitive skills that do not usually develop until early adolescence.
For this style of language learning, the later years of primary school are an ideal time to start, to maximise the balance between metacognitive skill development and the number of consecutive years of study available before the end of school.
SELF-GUIDED LEARNING BEST FOR ADULTS
There are, of course, some adults who decide to start learning a second language on their own.
They may buy a book, sign up for an online course, purchase an app or join face-to-face or virtual conversation classes.
To succeed in this learning context requires a range of skills that are not usually developed until adulthood, including the ability to remain self-motivated.
Therefore, self-directed second language learning is more likely to be effective for adults than younger learners.
HOW THESE INSIGHTS CAN BE APPLIED TO EDUCATION
In terms of the development of language proficiency, the message is fairly clear.
If it is possible to provide lots of exposure to rich language use, early childhood is better.
If the only opportunity for the learning of a second language is through more traditional language classes, then late primary school is likely to be just as good as early childhood.
However, if language learning relies on being self-directed, the attempt is more likely to be successful after the learner has reached adulthood.
•The writer is Associate Professor of Applied Linguistics, University of Southern Queensland.
•This article first appeared in The Conversation at http://theconversation.com , a website which carries analysis by academics and researchers.