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Cognition, ageing, and bilingualism: Investigating age-related changes in bilingual language switching and use.

Periodic Reporting for period 1 - CAB (Cognition, ageing, and bilingualism: Investigating age-related changes in bilingual language switching and use.)

Reporting period: 2017-09-01 to 2019-08-31

Over half of the European population speaks a second language. In an ageing society, it is thus important to understand how younger and older adults use multiple languages. The main aim of this project was to assess bilingual language control and switching in younger and older adults. Bilinguals need to monitor their surroundings to choose a language, ensure that they speak that language and not their other language, and sometimes switch between languages. Exactly how they achieve this, however, depends on the language context. Most previous work on bilingual language control has focused on more demanding contexts, for example by instructing bilinguals which language to use and when to switch. In bilingual societies such as the Basque Country (where this research was carried out), however, it is common for bilinguals to freely switch between their languages. The current research therefore focused on the role of context.

The main questions assessed in this project were:

1. How do bilinguals use their languages in different interactional contexts?
2. How does age affect bilingual language control?
3. How does bilingual language control relate to cognitive control?
4. What are the neural mechanisms underlying bilingual language control?
1. How do bilinguals use their languages in different interactional contexts?

We asked Spanish-Basque bilinguals to name pictures in different conditions. In single-language contexts, all pictures were named in the same language. In the voluntary task, bilinguals freely chose a language and switched when convenient. In the cued task, the two languages had to be used interchangeably in response to cues. This required more effort than naming pictures in a single-language context (‘mixing cost’). In contrast, when they could freely use two languages, bilinguals were faster than in a single-language context (‘mixing benefit’). This shows that the effort related to bilingual language control depends on the context. In addition, language choice was highly individual and related to personal preferences as well as speed of lexical access.

2. How does age affect bilingual language control?

Older (mean age: 68) and younger (mean age: 27) Spanish-Basque bilinguals named pictures in voluntary and cued tasks. In the cued task, older adults had more difficulties than younger adults to use two languages and to switch. In the voluntary task, older adults showed a larger switching cost but a comparable mixing benefit. Older bilinguals had greater difficulty using two languages in response to external cues, but freely using two languages might be easier than having to use one language for both age groups.

3. How does bilingual language control relate to cognitive control?

We also assessed whether bilinguals with better inhibition skills were also better at controlling their languages and switching between them. In a large sample of younger adults, we observed some correlations between the ability to switch languages and verbal inhibition. In the older adults, we did not observe this relationship. While there might be some similarities between language control and cognitive control, there are also many differences.

4. What are the neural mechanisms underlying bilingual language control?

Using fMRI, we investigated which brain regions are involved in bilingual language control in single-language contexts versus voluntary contexts. We are currently analysing the results of this project.
Understanding how younger and older adults use two languages is becoming increasingly important in our ageing and multilingual society. Previous research has mainly focused on the ability to control two languages in response to external language cues. This, however, does not represent bilinguals living in bilingual societies that can (at least sometimes) switch freely. The current research project therefore examined bilingual language control in different contexts, including voluntary versus cued language switching. At a theoretical level, this research increases our understanding of bilingualism and the cognitive and neural mechanisms underlying bilingual language control. By assessing this topic in younger and older adults, the research also improved our knowledge of age-related changes in bilingualism and language production. This research is of importance for the European society, especially considering that over half of its population speaks more than one language. At a local level, it is of great importance for the Basque Country (the region in which this research was carried out). The Basque Country is a bilingual society in which language switching is a common feature. Our research helps to better understand how and why bilinguals switch between languages, which can be used to guide language policies and multilingual education. In addition, language deficits have been argued to potentially be an early marker of diseases such as dementia. A better understanding of healthy age effects will contribute to future work assessing how language deficits can be used to reach a faster and more reliable diagnosis in bilinguals.