English only? Monolinguals in linguistically diverse contexts have an edge in language learning.

Accumulating evidence shows how language context shapes bilingual language use and its cognitive consequences. However, few studies have considered the impact of language context for monolinguals. Although monolinguals' language processing is assumed to be relatively stable and homogeneous, some research has shown novel learning through exposure alone. Monolinguals living in linguistically diverse contexts regularly overhear languages they do not understand, and may absorb information about those languages in ways that shape their language networks. The current study used behavioral and ERP measures to compare monolinguals living in a linguistically diverse environment and a unilingual environment in their ability to learn vowel harmony in Finnish. Monolinguals in both contexts demonstrated similar learning of studied words; however, their ERPs differed for generalization. Monolinguals in the diverse context revealed an anterior late positivity, whereas monolinguals in the unilingual context showed no effect. The results suggest that linguistic diversity promotes new language learning.