Bilingual Children Shift and Relax Second-Language Phoneme Categorization in Response to Accented L2 and Native L1 Speech Exposure.

Listeners adjust their perception to match that of presented speech through shifting and relaxation of categorical boundaries. This allows for processing of speech variation, but may be detrimental to processing efficiency. Bilingual children are exposed to many types of speech in their linguistic environment, including native and non-native speech. This study examined how first language (L1) Spanish/second language (L2) English bilingual children shifted and relaxed phoneme categorization along the cue of voice onset time (VOT) during English speech processing after three types of language exposure: native English exposure, native Spanish exposure, and Spanish-accented English exposure. After exposure to Spanish-accented English speech, bilingual children shifted categorical boundaries in the direction of native English speech boundaries. After exposure to native Spanish speech, children shifted to a smaller extent in the same direction and relaxed boundaries leading to weaker differentiation between categories. These results suggest that prior exposure can affect processing of a second language in bilingual children, but different mechanisms are used when adapting to different types of speech variation.