Your textbook reviews johnson and newport's study of the english proficiency of korean and chinese immigrants in the united states. the study demonstrated that knowledge of english grammar was associated with

The Critical Period affects language acquisition of a target language.

Explanation:

Jacqueline Johnson and Elissa Newport put out a study entitled : Critical Period Effects in Second Language Learning: The Influence of Maturation State in the Acquisition of English as a Second Language. Here, they point out how the age affects the language acquisition of Chinese and Korean English Language Learners. The younger the language learners are, the more adept they are in acquiring the target language. The study included acquisition of English grammar knowledge.