I'm sitting in my kitchen in London, trying to figure out a text message from my brother. He lives in our home country of Germany. We speak German to each other, a language that's rich in quirky words, but I've never heard this one before: fremdschämen. 'Stranger-ashamed'?
I'm too proud to ask him what it means. I know that eventually, I'll get it. Still, it's slightly painful to realise that after years of living abroad, my mother tongue can sometimes feel foreign.
Most long-term migrants know what it's like to be a slightly rusty native speaker. The process seems obvious: the longer you are away, the more your language suffers. But it's not quite so straightforward.
In fact, the science of why, when and how we lose our own language is complex and often counter-intuitive. It turns out that how long you've been away doesn't always matter. Socialising with other native speakers abroad can worsen your own native skills. And emotional factors like trauma can be the biggest factor of all.
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It's also not just long-term migrants who are affected, but to some extent anyone who picks up a second language.
"The minute you start learning another language, the two systems start to compete with each other," says Monika Schmid, a linguist at the University of Essex.
Schmid is a leading researcher of language attrition, a growing field of research that looks at what makes us lose our mother tongue. In children, the phenomenon is somewhat easier to explain since their brains are generally more flexible and adaptable. Until the age of about 12, a person's language skills are relatively vulnerable to change. Studies on international adoptees have found that even nine-year-olds can almost completely forget their first language when they are removed from their country of birth.
But in adults, the first language is unlikely to disappear entirely except in extreme circumstances.
For example, Schmid analysed the German of elderly German-Jewish wartime refugees in the UK and the US. The main factor that influenced their language skills wasn't how long they had been abroad or how old they were when they left. It was how much trauma they had experienced as victims of Nazi persecution. Those who left Germany in the early days of the regime, before the worst atrocities, tended to speak better German - despite having been abroad the longest. Those who left later, after the 1938 pogrom known as Reichskristallnacht, tended to speak German with difficulty or not at all.
"It seemed very clearly a result of this trauma," says Schmid. Even though German was the language of childhood, home and family, it was also the language of painful memories. The most traumatised refugees had suppressed it. As one of them said: "I feel that Germany betrayed me. America is my country, and English is my language."
Such dramatic loss is an exception. In most migrants, the native language more or less coexists with the new language. How well that first language is maintained has a lot to do with innate talent: people who are generally good at languages tend to be better at preserving their mother tongue, regardless of how long they have been away.
But native fluency is also strongly linked to how we manage the different languages in our brain. "The fundamental difference between a monolingual and bilingual brain is that when you become bilingual, you have to add some kind of control module that allows you to switch," Schmid says.
Mingling with other native speakers actually can make things worse
She gives an example. When she looks at the object in front of her, her mind can choose between two words, the English 'desk' and the German 'Schreibtisch' (Schmid is German). In an English context, her brain suppresses 'Schreibtisch' and selects 'desk', and vice versa. If this control mechanism is weak, the speaker may struggle to find the right word or keep slipping into their second language.
Mingling with other native speakers actually can make things worse, since there's little incentive to stick to one language if you know that both will be understood. The result is often a linguistic hybrid.
In London, one of the world's most multilingual cities, this kind of hybrid is so common that it almost feels like an urban dialect. More than 300 languages are spoken here, and more than 20% of Londoners speak a main language other than English. On a Sunday stroll through the parks of North London, I catch about a dozen of them, from Polish to Korean, all mixed with English to varying degrees.
Stretched out on a picnic blanket, two lovers are chatting away in Italian. Suddenly, one of them gives a start and exclaims: "I forgot to close la finestra!"
In a playground, three women are sharing snacks and talking in Arabic. A little boy runs up to one of them, shouting: "Abdullah is being rude to me!" "Listen…" his mother begins in English, before switching back to Arabic.
Switching is of course not the same as forgetting. But Schmid argues that over time, this informal back-and-forth can make it harder for your brain to stay on a single linguistic track when required: "You find yourself in an accelerated spiral of language change."
Laura Dominguez, a linguist at the University of Southampton, found a similar effect when she compared two groups of long-term migrants: Spaniards in the UK and Cubans in the US. The Spaniards lived in different parts of the UK and mostly spoke English. The Cubans all lived in Miami, a city with a large Latin American community, and spoke Spanish all the time.
"Obviously, all of the Spanish speakers in the UK said, 'Oh, I forget words.' This is typically what people tell you: 'I have difficulty finding right word, especially when I use vocabulary that I learned for my job'," Dominguez says. As a Spaniard who has spent most of her professional life abroad, she recognises that struggle, telling me: "If I had to have this conversation in Spanish with a Spanish person, I don't think I could do it."
Her theory is that the more familiar another language or dialect is, the more likely it is to change our native language
However, when she analysed her test subjects' language use further, she found a striking difference. The isolated Spaniards had perfectly preserved their underlying grammar. But the Cubans - who constantly used their mother tongue - had lost certain distinctive native traits. The key factor was not the influence of English, but of Miami's other varieties of Spanish. In other words, the Cubans had started to speak more like Colombians or Mexicans.
In fact, when Dominguez returned to Spain after her stay in the US, where she had many Mexican friends, her friends back home said she now sounded a little Mexican. Her theory is that the more familiar another language or dialect is, the more likely it is to change our native language.
She sees this adaptability as something to celebrate - proof of our inventiveness as humans.
"Attrition is not a bad thing. It's just a natural process," she says. "These people have made changes to their grammar that is consistent with their new reality… Whatever allows us to learn languages also allows us to make these changes."
It is nice to be reminded that from a linguist's point of view, there is no such thing as being terrible at your own language. And native language attrition is reversible, at least in adults: a trip home usually helps. Still, for many of us, our mother tongue is bound up with our deeper identity, our memories and sense of self. Which is why I for one was determined to crack my brother's mysterious text about 'fremdschämen' without any outside help.
To my relief, I figured it out pretty quickly. Fremdschämendescribes the sensation of watching someone do something so cringeworthy that you are embarrassed on their behalf. Apparently, it's a popular word and has been around for years. It just passed me by, like countless other trends back home.
After 20 years abroad, I shouldn't be surprised by this. Still, I have to admit that there is something a bit sad about my own brother using words I no longer understand; a hint of loss, perhaps, or unexpected distance. There's probably a German word for that, too. But I'll need a bit more time to recall it.
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