There is conflicting evidence for the influence of bilingual acquisition on early language development. This could be due to a lack of complete understanding of what factors are involved in bilingual development. One such factor is the sociolinguistic environment that bilinguals are raised in. This thesis aims to explore the influence of a native bilingual environment on early bilingual language development.
Chapter 1 explores the literature on language development in bilingual children. Experiential factors such as immigration status and the sociocultural position of the two languages in the environment, appear to influence bilingual language development. In Wales, there are two native languages, and the original native language is the minority one. However, there are efforts to increase the prevalence of bilingual speakers of Welsh. This results in a consistent amount of exposure to the minority language within schools and the community, which is unlikely to be there for other minority languages in bilingual UK populations. It is not fully understood how experiential factors such as language exposure contribute to and influence early language development in bilingual infants, and what this suggests for bilingual development overall. The goal of the following two chapters of this thesis is to further investigate these questions.
Chapter 2 investigates how speech segmentation develops in bilinguals learning two languages with conflicting rhythmic cues. Bilingual Welsh/English and monolingual Welsh and English infants between 7- and 11-months-old were recruited. The infants’ ability to segment continuous English sentences based on stress-initial (trochaic) word prosody was tested using a familiarisation-test Event-Related-Potential (ERP) paradigm. Both English and Welsh have a predominantly trochaic prosody on bisyllabic words, but other rhythmic information such as vowel elongation occurs on different syllables in the two languages. This latter fact results in the prosodic pattern being harder to detect in Welsh than in English. Research has shown that infants rely on prosodic cues to learn word boundaries in continuous speech, and differences in languages’ prosodic patterns influence the age at which segmentation skills emerge. Little is known about how bilingual infants deal with dual language exposure in order to acquire both of their languages’ prosodic patterns and develop segmentation skills in each language. As such, the studies in this chapter sought to answer questions about bilingual speech segmentation, and the influence of language exposure on its emergence. No differences in the development of segmentation skills were found between bilingual Welsh/English and monolingual English children, and English exposure was found to be necessary for English speech segmentation.
The results of Chapter 2 suggest that one of the building blocks for vocabulary acquisition, speech segmentation, develops at a similar rate in bilingual Welsh/English children and their monolingual peers. It could be that contrary to the majority of literature on bilingual vocabulary development, bilingual Welsh/English infants also develop their English vocabularies at a similar rate to monolingual English peers. This was explored in Chapter 3, where vocabulary measures were taken from over 200 infants between 10- and 28-months old, exposed to only English or Welsh, or both languages. In line with the results from Chapter 2, bilingual Welsh/English infants had similar English vocabularies to their monolingual English peers, and larger combined (English + Welsh) vocabularies. The most influential factor on their vocabulary development was exposure to the dominant language in the environment – English. The implications of how this could inform Welsh language exposure are discussed.
In Chapter 4, the implications of the findings are discussed. In environments like Wales, there is a highly prevalent bilingual culture but English is the dominant language. It seems that as long as bilingual babies receive ambient English from the environment, they develop similarly to their monolingual peers, and even have an early advantage for vocabulary development. Furthermore, although English exposure influences both English and Welsh vocabulary size, Welsh exposure only influences Welsh vocabulary size. Overall, these findings imply that environmental factors such as language exposure influence bilingual language development differently depending on sociolinguistic contexts like having a native bilingual community.