Studies on bilingual speech processing have implied that bilinguals may either have two separate or one intertwined system. These findings have been obtained by multiple methods using various types of bilinguals. Our study compared monolinguals and two types of bilinguals. We used the same methods for all groups, i.e., we measured attentive identification scores and preattentive discrimination. Our results show that bilinguals process speech sounds differently from monolinguals, and more importantly, that there is a difference between the two types of bilinguals. We suggest that dominant bilinguals have two separate phonological systems, while balanced bilinguals have one uniform system.
Index Terms. speech perception, bilingualism, mismatch negativity