The impact of regional accent variation on monolingual and bilingual infants’ lexical processing

Phonetic variation is inherent in natural speech. It can be lexically relevant, differentiating words, as well as lexically irrelevant indexical variation, which gives information about the talker or context, such as the gender, mood, regional or foreign accent. Efficient communication requires perceivers to discern how lexical versus indexical sources of variation affect the phonetic form of spoken words. While ample evidence is available on how children acquiring a single language handle variability in speech, less is known about how children simultaneously acquiring two languages deal with phonetic variation. This thesis investigates how the bilingual language environment affects children’s ability to accommodate accented speech. We consider three hypotheses. One is that bilingual infants may have an advantage relative to monolinguals due to their greater experience with phonetic variability across their two phonological systems. This is because the lexical representations in bilingual children, who have more experience with accent variation than monolingual children, might be more open to phonetic variation than monolinguals. Representations that are more open to variation might lead to higher flexibility in the word recognition of children with multi-accent input (bilinguals), resulting in accommodation benefits when processing an unfamiliar accent. An alternative hypothesis, however, is that bilingual children may have less stable lexical representations than monolinguals because their vocabulary size in each language is smaller. This could lead to processing costs in accent adaptation, resulting in accommodation disadvantages for bilinguals. The third and final hypothesis is that there would be no difference between bilinguals and their monolingual peers. This is because the effects of greater accent experience but less stable lexical representations in bilinguals may essentially neutralise each other, resulting in equivalent accent accommodation by bilinguals and monolinguals. To evaluate these hypotheses, three experiments were conducted with 17- and 25-month-old bilingual and monolingual children. Their ability to accommodate unfamiliar accented speech was analysed based on their language experience, pre-exposure to the unfamiliar accent, the type of phonetic variation (easy versus difficult phonetic change), and the cognitive demands of the experimental procedure. Taken together, the findings of Experiments 1-3 suggest that bilingual language input neither benefits nor hampers accent adaptation in bilingual children relative to monolingual children. The results carry implications for our current understanding of bilingualism and phonological development