Adopted children retain unconscious knowledge of forgotten birth language

Do adopted children forget everything they have learned about their native language when they learn their new language? Or is knowledge about that language still hidden somewhere in the brain? New research by linguists Wencui Zhou, Anne Cutler and Mirjam Broersma on Dutch children who were adopted from China shows that abstract knowledge persists.

A child who is adopted from another country will usually learn the new language quickly. Although that almost goes without saying, what this child does is unique, says Mirjam Broersma, associate professor of linguistics at Radboud University. ‘The child had started learning a language, that process is suddenly completely interrupted and then it starts a completely new language development. That is fascinating, especially because it goes so well: in a very short time they can no longer be distinguished from children who learn that language from birth.'

But what happens to the language they were learning before adoption? Earlier research by Broersma among Dutch adults who were adopted from Korea showed that although there is no longer conscious knowledge of the birth language, there is unconscious, abstract knowledge that makes it easier to (re)learn speech patterns in that language. This aroused the curiosity of Broersma and two fellow researchers: do recently adopted children still have direct access to knowledge of their birth language, or has it already subsided and is it only accessible when learning the sounds of the birth language again?

Unconscious knowledge

The new study by Broersma and fellow linguists Wencui Zhou (Tilburg University Language Centre) and Anne Cutler (Western Sydney University, Australia) shows that even young children, who have been in their new country for a relatively short time, only have unconscious knowledge of their birth language. In their study, they examined 46 Dutch children (4-10 years) who were adopted more than one but less than ten years ago from the Cantonese- or Mandarin-speaking part of China. They were compared with 47 non-adopted Dutch children and 40 non-adopted Chinese children.

The children followed ten training blocks in the presence of their parents, in which they learned to identify Chinese sounds and tones. Chinese is a so-called tonal language, in which the pitch and change in tone are crucial for the meaning of words or syllables. In a game with dinosaurs and pandas, the children judged which baby dinosaur or baby panda was the best in imitating its Chinese dinosaur or panda mother. In another part of the study, the children had to imitate the speech contrasts themselves, by imitating the mother panda or dinosaur. Native speakers of Cantonese or Mandarin Chinese then checked how good that pronunciation was. ‘We were a bit nervous, because they were long sessions for such young children,’ says Broersma. ‘We assumed we would have a lot of dropouts, but that didn't happen. All of the children completed everything.’

Same pattern

In the part of the study where the children had to assess the pronunciation, the adopted children initially recognised the sounds just as poorly as the Dutch control group. But with training, that skill came back and the adoptive group got better and better, while the control group didn't. The adopted children thus show the same pattern as the adults who were adopted from Korea. ‘It is very interesting that they are already so focused on Dutch that they need retraining to 'pick up' Chinese again. That shows how quickly the switch from Chinese to Dutch took place’, says Broersma.

Nuances in pronunciation

Something surprising happened in the imitation part of the study: the imitations of the adopted children were already better than those of the children born in the Netherlands at the start of the training. They were able to make nuances in their pronunciation, while the control group could not, even before they had been trained to do so. Broersma. ‘It shows that the adopted children have a sense of how tone actually works and what you should pay attention to when producing it. The same goes for the 'ts'-like sounds – so-called affricates – that we don't have in Dutch either.’ The children can only have developed that feeling from their exposure to Chinese, because in Dutch these specific sound and tonal differences do not exist. It is striking that the adults from the earlier study no longer had that feeling.

Touched by outcomes

The research by Broersma, Zhou and Cutler thus shows that children acquire abstract information from a language from a very early age, and subconsciously retain this knowledge, even if they no longer use it. Broersma: 'That says a lot about memory: knowledge is not overwritten by new knowledge, but continues to exist in a certain abstract form.' The imitation results also show that knowledge about general properties of the native language, such as tone, is still available for very young adopted children, but no longer for adults.

There is another important added value of this research, says Broersma. ‘When we research adopted people, we always notice that they – or their parents – are extremely curious about what remains of the experiences they have gained before their adoption. Some participants of our Korean study were really touched by the results: ‘Gosh, so there is knowledge from before my adoption, which still partly determines who I am.’ With this study we show that – in terms of language memories – that feeling is correct: you still have knowledge from before your adoption somewhere in your brain.'

The article Asymmetric memory for birth language perception versus production in young international adoptees was recently published in the scientific journal Cognition.

Photo: Kindel Media