Bilingual language control during single-language production: does relocation to a new linguistic environment change it?

A bilingual's two languages are simultaneously active and competing for selection, even when only one language is used. To manage this competition, bilinguals apply language control. We examined how bilinguals apply control across two single-language tasks and how this language control might adapt to the language environment bilinguals live in. We conducted a longitudinal study with Mandarin-English bilinguals who moved from China to the UK and a control group staying in China. Participants completed a picture-naming task and a verbal-fluency task twice, approximately seven months apart. We examined language order effects by comparing performance in each language when it was used first versus after the other language. While the L2 benefited from being used second, L1 performance benefited less or even deteriorated after L2 use. This suggests bilinguals proactively applied language control, especially during L2 use, to manage the anticipated language competition from the L1. However, these effects did not change after relocation to the UK, nor did they differ between the groups. This suggests that while language control is a core part of language production, the language environment a bilingual lives in might not have a defining impact on the exact way this language control is applied.