عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Some scholars have argued that there is a negative correlation between the onset age of L2 acquisition and performance on different measures of L2 knowledge. A kind of biological scheduling is assumed to be responsible for this maturational constraint on language development. The present study asks whether and to what extent critical period effects can be found for universal properties of language considered to be innate. Subjacency, Empty Category Principle (ECP) or That-trace effect, and Structure Dependency are the linguistic properties that are investigated in this study. The results indicated a very adverse powerful effect of the increase of onset age on the ability of the learners to detect UG violations. Moreover, age differences were also important in that early learners, the 3-9- year olds, always performed as well as the native speakers; the 10-16-year olds could not perform as well as the native speakers in most cases; and late learners, the 17-36-year olds failed to perform as well as the native speakers and early learners in any of the issues under investigation. It is concluded that (a) the ultimate level of attainment depends in part on the onset age (b) there are sensitive periods controlling language development during which the acquisition of different linguistic properties is fruitful and after which language learning becomes irregular and incomplete (c) the age-related loss in performance is cumulative and there is no cut off point. Thus, the age of onset has a significant effect on ultimate achievement of L2 learners.