A third of the way through this absorbing and engagingly written book, Albert Costa describes a family meal: “The father speaks Spanish with his wife and his son, but uses Catalan with his daughter. The daughter in turn speaks Catalan with her father but Spanish with the rest of the family, including the grandmother, who only speaks Spanish though she understands Catalan.” It’s what Costa calls “orderly mixing”, and, depending on which restaurants you visit, a common enough situation: everyone is bilingual here, but the language used changes according to who it is directed at. Given that everyone at the table understands both languages, would it not be easier and less confusing if everyone just chose one language and stuck to it? That sounds logical, but the bilingual mind doesn’t work that way. If you do not believe it, Costa suggests “having a conversation with a friend in the language you do not usually use and see how far you get”.
Not far, he observes. And Costa should know – not just because he was an expert in language acquisition (he died last year), but because the family he is describing is his own. One of the reasons this book makes sense of its complex material – from basic code-switching tests to the latest technology in brain imaging and transcranial magnetic stimulation – is that Costa is such a charming and witty guide. This is a rigorous book about complex science, and much of it could have been intractably technical or riddled with statistics. But Costa has a winningly informal style, a deadpan wit, and mixes laboratory findings of cognitive neuropsychology with examples from everyday life, TV programmes, sports and politics. In one set of cognitive tests, he shows how people are more risk-averse in their second language, and more gung-ho in their first. Costa suggests the practical applicablity of such research by advising us to visit casinos where people speak a language we are less comfortable in – it substantially reduces the likelihood of our going home shirtless and barefoot.
The family, of course, is where it all starts. As children growing up with a French-speaking mother and an English-speaking father, my sister and I would never have dreamed of speaking English to our mother and French to our father. When we were forced to, out of politeness or in social contexts, it felt instinctively wrong and against the grain. As for our parents, they only ever spoke to each other in French – they met in Liège in the 1960s – even though they lived for decades in Raynes Park, south-west London. Although everyone spoke two languages, no one spoke both languages to each other, and the lines were never crossed. The reasons for this had nothing to do with practicality or logic or economies of meaning. They were at once the most complex and the most basic questions of who we are when we speak, and which version of ourselves we become when we choose, or think we choose, a language.
Costa’s book starts in the womb. The human ear is already fully developed at around 20 weeks, which means the newborn baby has heard the world long before it has seen it. Costa describes how, during the “pre-natal bilingual experience”, the bilingual baby is already able to differentiate between languages – not just between the mother’s language and other languages, but between its two “home” languages and others. “Nine months in the womb go a long way,” Costa writes; he then tracks what happens in the bilingual cradle. One finding is that at eight months old the bilingual baby can discriminate between two different languages to which it has not been exposed. This facility isn’t simply to do with hearing, since how we interpret sounds depends on other stimuli, notably the movement of lips (the bilingual baby can differentiate just by watching videos of people speaking with the sound turned down). The ability to read visual clues and articulatory movements is already in place. For an enjoyably destabilising proof of how we “hear” by what we see, I recommend watching the audiovisual illusion called the McGurk effect (available on YouTube as a BBC science segment). Here, the same sound is produced by the same speaker but with different lip movements, thus visually tricking the brain into hearing a different sound. Even knowing that it’s an illusion doesn’t stop you mishearing the sound; the only way to hear it correctly it is not to watch the lips.
Costa also describes how a bilingual person’s two languages can be in productive conflict, and how, even though only one language might be being used at any given time, the second language is still being cognitively exercised. Less encouragingly, he also describes experiments with people who have forgotten a childhood language. We assume – at any rate, I did – that a language we once knew, or had some fluency in as children, remains lodged in our minds. But some tests on adults who were adopted as children and lost their native language show there is no mental record of their mother tongue. It is as if they had never known it. The phenomenon that Costa calls, in a different context, one language “eating” another, is widespread, albeit less drastic, and not always negative. “Interference”, for instance, is an ambiguous gift: while one language might disrupt the other – jam its frequencies, as it were – the context determines whether it’s advantageous or not. Think of the poetry of Paul Muldoon or Dylan Thomas, where the interference from Irish and Welsh is often at the heart of the poem – a rich fund of material, as well as perhaps an impetus to write in the first place. In a different context – telephone banking or a situation involving paramedics – interference is a problem.
Fifty years ago, there was a consensus – culturally enforced rather than scientifically supported – that bilingualism “confused” children. It’s hardly surprising that this consensus existed in Britain and, to an extent, France. The rest of the world barely even noticed that it was living bi- or multilingually, and got on with speaking one or two languages at home, another couple in school, and watching films or listening to music in yet more. The advantages of bilingualism, whether you come to it early or late, are discussed by Costa from various perspectives, not just the obvious ones such as agility and stimulation, learning for its own sake, access to other cultures, basic fluency on holiday, respecting your neighbours in your new Welsh cottage or Provençal dream home.
Costa twice quotes Nelson Mandela’s famous comment that when you talk to someone in their first language, your message goes to their heart; talk to them in their second and it goes to their head. We don’t need tests to tell us that greeting people, however ineptly, in their native language, rather than talking to them loudly and slowly in English as if they were stupid, will make them feel differently about us. But it’s fascinating to see the cognitive mapping behind it.
Costa goes on to discuss the long-term benefits to brain health of the exercise the mind does with language. It is what he calls “cognitive savings”, which work like (another analogy of his) a “pension” that makes the brain more resilient in ways that help it delay the ill-effects of ageing and stave off dementia. Those benefits are available late in life too – it doesn’t matter when you start a new language, or indeed what language you choose. Learning a second language gives you “cognitive reserves” that your brain continues to draw on.
A regular excuse some monoglots make for not learning a language is that it’s not “useful” because “everyone speaks English”. Happily, this is far from true, but the truer it is, the worse it is for the anglo-monoglot, because, as this book shows us, scientifically but also culturally, all languages are useful, and it doesn’t really matter which second language you learn, or indeed when. It is concerned with what happens to our brains, from cradle to grave (sometimes via the nursing home, where several of Costa’s tests are conducted), when we acquire another language. It turns out that opening our minds and preserving them are symbiotically linked.
• The Bilingual Brain: And What It Tells Us About the Science of Language by Albert Costa, translated by John W Schwieter, is published by Allen Lane (RRP £20). To order a copy go to guardianbookshop.com. Free UK p&p over £15.