Highly proficient bilinguals implement inhibition: Evidence from n-2 language repetition costs

Several, but not all, models of language control assume that highly proficient bilinguals implement little to no inhibition during bilingual language production. In the current study, we tested this assumption with a less equivocal marker of inhibition (i.e., n-2 language repetition costs) than previous language switching studies have. N-2 language repetition costs denote worse performance when switching back to a recently abandoned language (i.e., worse performance in ABA language sequences than CBA sequences, where A, B, and C refer to different languages). Whereas this marker has solely been used to investigate second-language learners in prior studies, we examined highly proficient bilinguals. The results showed that substantial n-2 language repetition costs can be observed with highly proficient bilinguals. Moreover, this inhibition effect was substantial for all 3 languages, but larger for the 2 dominant languages (Turkish and German) relative to the less proficient language (English). These findings indicate that even highly proficient bilinguals implement inhibition to restrict language production to the target language.