Ultimate attainment in L2 inflection: Performance similarities between non-native and native speakers

This paper reports four experiments that test whether persistent problems of second-language (L2) learners with L2 inflection, such as case or subject–verb agreement, are the consequence of age-related grammatical impairment of L2 morphosyntax or differences in processing efficiency between natives and non-natives. Fifty-nine L1 English, Dutch and Russian advanced to near-native L2 speakers of German were tested on their ultimate attainment of case marking, subject–verb agreement and gender concord. Different off-line and on-line tasks were employed. Cross-linguistic and cross-experiment comparisons of native and non-native performance show that native-like ultimate attainment of L2 inflection is possible for postpubescent learners in L2 grammar and L2 processing. Non-target-like L2 inflection is systematically related to L1 transfer and limitations in L2 processing efficiency. In conjunction, these findings argue against a critical period for morphosyntax in L2 acquisition; rather, they suggest that non-native and native grammars and processing systems are fundamentally identical, with L2 systems being computationally less efficient due to L1 influence.