||Kim, Hye Jeong. (2015). The effects of learner-centered cooperative activities on learners' understanding of English sentence structure. The Linguistic Association of Korea Journal, 23(2), 53-69. This study examines the effects of a cooperative activity on learners' understanding of structure of sentences. It is not easy to carry out a group activity in classes on the principles of syntax. This study suggests cooperation among group members for sharing information necessary for analyzing structure of sentences. To examine the impact of this cooperative activity, control and experimental groups were treated with different factors. The control group focused on providing syntactic information through a lecture by the professor and students' presentation. The experimental group focused on interchanging opinions and joining a discussion through cooperative activities. The results of the tests showed that cooperative activities have a positive effect on understanding of the structure of sentences. Additionally, students got used to cooperation, which makes it easier to analyze and understand the structure of sentences.