Speech and language therapy (SLT) services are coming under increased pressure to provide people living in linguistic minority communities with assessment and intervention in the language of the community in which the client lives. In Ireland, Irish, although a minority language, enjoys a positive attitude and a high status as the first official language of Ireland. However, there is little known about Irish language acquisition in typically developing children, let alone assessment or developmental pathways for speech and language therapists to work with. Furthermore, the study of Irish can make a valuable contribution to cross-linguistic research as it has structures which are very different to English such as a VSO word order, and complex morphophonological inflections in its initial mutations.
This study adapted a well-known research tool, the MacArthur-Bates Communicative Development Inventories, to Irish in order to measure vocabulary and grammatical development longitudinally for twenty-one children aged between 16 and 40 months. Results from the parent-checklists were validated against spontaneous language samples and elicitation tasks, and compared to crosslinguistic studies of early language development. The analysis explored theoretical questions such as whether there is a ‘noun advantage’ in Irish, how grammar is acquired, and the nature of the relationship between the lexicon and grammar. In addition, other theoretical aspects such as the effect of gender, birth order and maternal education on early language milestones were investigated. The findings indicate that Irish-speaking children develop vocabulary at a relatively similar rate to other children but the content of their vocabulary is somewhat different, with a relative advantage in grammatical words once they have 400 words in their vocabulary. On the other hand, many inflectional morphemes are acquired relatively late, and this is largely due to their relative complexity. The outcomes of this study not only give SLTs a descriptive framework of the development of vocabulary and grammar in Irish but also contribute to the body of cross linguistic research.