Grammatical development in adolescent first-language learners*

Studies of first-language acquisition in adolescence are very rare and depend primarily on comprehension measures to evaluate grammatical knowledge. These studies have led to the general conclusion that grammatical development in adolescence is severely impaired and performance is highly variable both within and across individuals. This article is the first to present longitudinal production data on two deaf adolescents as they are acquiring their first language, American Sign Language (ASL), at the ages of 12;1 and 13;7. Analyses of the production of two complex predicate types indicate that these individuals made consistent progress in the acquisition of these structures during the first 31 months of their exposure to ASL. A subsequent study investigates their comprehension abilities after seven years’ exposure to ASL and reveals similar disruptions in comprehension relative to other adult signers who learned ASL in adolescence. However, the degree of disruption varies with the level of processing demands. One explanation of the data is that adolescent first-language learners are particularly sensitive to performance factors and can only show their knowledge of language under ideal conditions. This implies that adolescent first-language learners continue to suffer from linguistic isolation even after being exposed to language because they cannot process the language efficiently enough to recognize patterns in the input under normal conditions. According to this view, deficits in performance relative to native signers are due not solely to lack of grammatical competence, but to closely related problems in processing.