In general, the difference in proficiency between child and adult learners of a second language is remarkable. This difference has inspired researchers in different fields for decades and has lead to the formulation of the Critical Period Hypothesis for second language acquisition. According to this hypothesis, a high level of proficiency should not be attainable for late learners due to a biologically determined decrease in sensitivity to language input after puberty.

The huge variation in ultimate attainment in many late learner groups in earlier studies, has recently evoked an interest in the question of whether there are individual late learners who manage to achieve a native level of proficiency in a second language.

In this dissertation, this question is investigated for the area of syntax and related to the typological distance between native and target languages. In this study, a sentence preference task and an imitation task were used to test highly proficient German, French and Turkish late learners of Dutch on their command of dummy subject constructions, for which no explicitly formulated rules are available. The use of these tasks and constructions and the important role for the typological distance between languages make the design of this study truly unique.

The results presented in this dissertation are not only relevant to second language researchers, but also to neurolinguists, psycholinguists and all late second language learners who want or need to reach an extremely high level of proficiency in the target language.