Being bilingual doesn’t improve cognitive ability

Some of the advantages of growing up bilingual have been overstated, a large study has revealed.

People who learn a second language during childhood enjoy a clear and uncontested benefit in being able to communicate to a greater number of people than those who learn only one.

However, researchers are at odds over whether being bilingual aids in other ways – particularly, in higher level brain functions.

Some studies have reported that bilingual people are better at executive functions – the cognitive ability to exercise voluntary control over thoughts and behaviours. Executive functions include maintaining attention, controlling inhibitions, resolving conflicts and task switching.

For instance, a 2008 study testing executive function in kindergarten kids found that it was at its most efficient in children who grew up speaking two languages at home – in this case, English and Spanish. English-speakers who learned Spanish once they attended kindergarten also had better test results than children who spoke only English.

That and a couple of other studies that found similar results among other bilingual pairings have become controversial, however, with several follow-up projects unable to repeat the result.

Sample sizes have been often cited as one reason findings haven’t been replicated. A 2015 meta-analysis of previously published work concluded that 80% of tests in the field returned inconclusive results, and the remaining 20% didn’t involve enough children to rise above chance.

“The cumulative effect of confirmation biases and common research practices has either created a belief in a phenomenon that does not exist or has inflated the frequency and effect size of a genuine phenomenon that is likely to emerge only infrequently and in restricted and undetermined circumstances,” the authors concluded.

Now, a study that directly tested more than 4500 children has reached a similar conclusion.

The research, led by Anthony Steven Dick of Florida International University, US, is published in the journal Nature Human Behaviour.

Dick and his colleagues tested 4524 volunteers aged between none and 10, in what they describe as a “demographically representative sample” spread across the United States.

“There is little evidence for a bilingual advantage for inhibitory control, attention and task switching, or cognitive flexibility, which are key aspects of executive function,” they conclude.

Their results did, however, reproduce another frequent finding of previous studies. Bilingual children tend to have smaller English vocabularies than those who spoke English exclusively.

However, the researchers are quick to assert that “these results should not be taken to endorse the idea that learning a second language is disadvantageous — it is in fact advantageous in a number of domains”.

The decrease in comparative vocab, they note, is “small to modest”, accounting for a difference of between just one and 5%.