The goal of this paper is to extend our knowledge on the basic argument: age of acquisition–proficiency correlations through the comments on Ellen Bialystok’s original paper--The structure of age: in search of barriers to second language acquisition. On such an objection, this paper tries to demonstrate three processes of comments: theoretical background of E. Bialystok’s paper; introduction to author’s critique; arguments supporting the claim that second-language(L2) acquisition is not to be significantly constrained by the age factor that circumscribe a critical period for native-like attainment. With the assessment of E. Bialystok’s research, this paper tends to make comments on the perspective of bilingualism approach. The goal of this paper is to extend our knowledge on the basic argument: age of acquisition-proficiency correlations through the comments on Ellen Bialystok’s original paper - The structure of age: in search of barriers to second language acquisition. On such an objection, this paper tries to demonstrate three processes of comments: theoretical background of E. Bialystok’s paper; introduction to author’s critique; arguments supporting the claim that second-language (L2) acquisition is not to be significantly constrained by the age factor that circumscribe a critical period for the native-like attainment. With the assessment of E. Bialystok’s research, this paper tends to make comments on the perspective of bilingualism approach.