The marker yypothesis: a constructivist theory of language acquisition

This thesis presents a theory of the early stages of first language acquisition. Language is characterised as constituting an instructional environment - diachronic change in language serves to maintain and enhance sources of structural marking which act as salient cues that guide the development of linguistic representations in the child's brain. Language learning is characterised as a constructivist process in which the underlying grammatical representation and modular structure arise out of developmental processes. In particular, I investigate the role of closed-class elements in language which obtain salience through their high occurrence frequency and which serve to both label and segment useful grammatical units. I adopt an inter-disciplinary approach which encompasses analyses of child language and agrammatic speech, psycholinguistic data, the development of a developmental linguistic theory based on the Dependency Grammar formalism, and a number of computational investigations of spoken language corpora. I conclude that language development is highly interactionist and that in trying to understand the processes involved in learning we must begin with the child and not with the end-point of adult linguistic competence