Where phonology meets morphology in the context of rapid language change and universal bilingualism: Irish initial mutations in child language.

As one of the Celtic languages, Irish is among the few languages in the world that employ word initial mutations (IMs) in order to express grammatical functions. IMs express grammatical information by a way of systematic alternation of minimal phonological contrasts, which closely links segmental phonology to grammatical morphology (Irish also employs final consonant palatalization as a grammatical marker, but this will not be the focus of our paper). The overwhelming majority of Irish speakers are bilingual (with English), and virtually all Irish-speaking children grow up with varying degrees of exposure to and use of English in the home. Irish is undergoing rapid language change at present, and the system of IM is affected by this process of shift such that many fluent Irish speakers show inconsistent use of IM in their spoken language. Given inconsistency in the use of a grammatical system in the adult language, the question arises whether it will be possible to identify developmental norms for the use of IM in child language. This in turn has clinical implications, in terms of the presence (or absence) of clinical markers of language delay or disorder. The data we report on consist of narrative samples from typically developing children (aged between 3 and 6) and a group of parents, who completed the same task (telling a story from a wordless picture book). We plot consistency and accuracy IM use in the language of children and parents. A key finding is that inconsistent IM use by parents is mirrored by inconsistent use by children. We discuss clinical implications for language sampling for diagnostic purposes, and the importance of individualized assessment.