Why bilingualism is best for children

Over half the world’s population speaks at least two languages, but little is known about how bilingualism affects the brain, partly as neurological research was confined for so long to brain damage caused by disease and injury. Developments in neuroimaging enabled wider application and it is now possible to watch live brain activity in healthy people.

In The Bilingual Brain, renowned neurolinguist Albert Costa considers studies from around the world, including regions where two languages are spoken habitually—such as his native Barcelona and Hyderabad, in southern India. The youngest participants were just two days old; brain activity was monitored as they slept, while stories played “normally” and backwards. Oxygen consumption in the brain suggested even very young babies recognise “normal” language patterns. By four months old, babies from bilingual homes would gaze at the mouth of a person speaking for longer than monolingual ones, suggesting that “the complexity of being exposed to two languages encourages babies to extract as much information from communicative acts as possible.”

The mental effort involved in task-switching, or suppressing the language not in use while the other is spoken, seems to confer all kinds of benefits as bilinguals progress through childhood and eventually to old age, with its risk of language loss. They may have better brain plasticity and increased ability to focus. One study finds people consider ideas more rationally when using acquired language because they don’t experience emotional triggers present in a mother tongue.

Lest things look too rosy for the bilingual, some studies show a very marginal difference, and there is still much work to be done, though sadly not by Costa, because he died in 2018. A clear and approachable study, The Bilingual Brain acquired some odd syntax in translation from Spanish to English, proving, perhaps, it is never easy to juggle languages.

The Bilingual Brain—And What It Tells Us about the Science of Language by Albert Costa, tr by John W Schwieter (Allen Lane, £20)