Automaticity of speech processing in early bilingual adults and children

We examine whether early acquisition of a second language (L2) leads to native-like neural
processing of phonemic contrasts that are absent in the L1. Four groups (adult and child
monolingual speakers of English; adult and child early bilingual speakers of English and
Spanish, exposed to both languages before 5 years of age) participated in a study comparing
the English /ɪ/ - /ε/ contrast. Neural measures of automatic change detection (Mismatch
Negativity, MMN) and attention (Processing Negativity, PN and Late Negativity, LN) were
measured by varying whether participants tracked the stimulus stream or not. We observed
no effect of bilingualism on the MMN, but adult bilinguals differed significantly from adult
monolinguals on neural indices of attention. The child bilinguals were indistinguishable
from their monolingual peers. This suggest that learning a L2 before five years of age leads
to native-like phoneme discrimination, but bilinguals develop increased attentional sensitivity
to speech sounds