In recent years a growing number of theoretical and empirical studies of first language acquisition have cast doubt on the hypothesis that acquiring language is a
deterministic process in which the role of experience is restricted to triggering innate principles of grammatical content. The aim of this thesis is to explore areas of
language where input -based learning demonstrably plays a role and to find learning
mechanisms that account for the construction of observed overgeneral grammars
and the process of their restriction.
The thesis is a comparative study of the acquisition of argument structure
in English and in Hungarian. The detailed analysis of spontaneous speech samples of two -- year -old children reveals that the omission of subjects, objects and
prepositions at the so- called telegraphic stage of English child language cannot be
explained either by limitations in processing capacity or by postulating an incomplete Universal Grammar. It is suggested that children's implicit arguments and
oblique noun phrases lacking case or prepositional marking need not be analysed as
syntactically ill- formed, since they conform to permissible abstract structural configurations. The errors may instead be attributed to overgeneral or indeterminate
rules of pragmatics, which are fuzzy and variable in the mature grammar.
It is shown that the nature of the children's intake of the primary linguistic
data is a good predictor of the nature and extent of overgeneralisation or indeterminacy and of the speed with which the rules are fine -tuned to match the target.