Indeterminacy in the grammar of adult language learners

This paper investigates the formal nature of the grammar formed by adult learners of English. Two groups of subjects were tested: native English speakers, and native Chinese speakers who arrived in the United States and learned English as adults. The adult learners resided in the United States for many years prior to testing and were therefore at an asymptotic level of performance in English. The question asked is whether adult learners are as consistent in their judgments as native speakers across two testing sessions. Both groups were given the grammaticality judgment task of Johnson and Newport (1989) twice, with three weeks between tests. While native speakers' performance was highly consistent across the two testings, adult learners' performance showed a marked degree of inconsistency. It is concluded that the grammars of the adult learners are not fully determinate, and that adult learners rely on other strategies for a substantial portion of their performance in their late learned language. Late language learning is thus different from native learning not only in the ultimate level of performance attained, but also in the nature of that knowledge.