Emergence of functional categories in bilingual first language acquisition
This thesis is a case study on the emergence of functional categories in bilingual first language acquisition. The investigation focuses on the transition from one-word to multiword utterances and the shaping of functional projections of Determiner, Agreement and Tense and their associated formal features. The empirical basis of this work is a corpus of thirty-nine videorecorded observations of Carlo, an English-Italian bilingual child, during free-play sessions with an adult. Data was collected separately for English and Italian for a period of fifteen months from when the child was 1;10 until he was 3;1, and was then transcribed in CHAT format. Four interrelated lines of enquiry inform the analysis presented here. The principal research question concerns the acquisitional strategies adopted by C. in these early stages of development in the two languages. A bilingual child is the closest one can get to a perfect matched pair where a number of variables such as socio-cognitive development, socio-economic status, parents' education, etc. are eliminated, and the two main variables to be investigated are the child's two input languages. This is an ideal situation in which the respective roles of general acquisitional strategies and language particular ones can be teased apart. An analysis of the emergence of the morphosyntactic correlates of Determiner, Agreement and Tense categories in English and Italian reveals a discrepancy between the two languages in the age of acquisition, rate of acquisition and in the language-specific strategies the child adopts. The observation of a significant difference in C.'s acquisitional strategies in English and Italian leads us to the second and third research questions: the way in which the emergence of functional categories differs between the two languages, and the reasons why this should be the case. The most obvious difference is the extent to which morphological correlates of functional categories emerge in the child's speech. In Italian, verbal and nominal morphology emerges earlier than in English and, at least in the nominal system, there is evidence that an Agreement category is part of the child's grammar. In English, verbal morphology is virtually non-existent by the end of the period of observation, and there is no substantial evidence that either Agreement or Tense are realised. Lexically-specific, item-based learning plays a substantial role in both languages, but in Italian there is some evidence that a number of grammatical contrasts are becoming productive by age 3;0, albeit some of them are still limited to a small number of lexical items. Two reasons were identified for the observed differences in the emergence of Determiner, Agreement and Tense in English and Italian: a typological reason, and an environmental reason. The former concerns the richness of Italian morphology, where grammatical contrasts are transparently marked both on nominal and verbal paradigms, as opposed to the relative poverty of English morphology where such contrasts correlate less obviously ans systematically with morphophonological markers. The latter reason concerns the very different input conditions in which C. is exposed to Italian and English: Italian is the home language spoken to him by his family and his babsysitters, while he is addressed in English by the staff at the nursery where one adult is in charge of several children and cannot engage in the one-to-one interaction which is typical of the dyadic situation in which C. finds himself at home. The differences observed in the lead-lag pattern between C.'s Italian and his English also provide sufficient evidence to address the fourth research question concerning the separate developement of the two languages. The analysis of the data did not reveal any systematic interferences from one language to the other. On the contrary there is evidence that C. is sensitive to the different morphosyntactic cues of his two input languages, and that he can treat the two as independent, self-contained problem spaces.