L1 interference is one of the important complicated issues in language transfer both at home and abroad. The author argues that we should study this issue from different points of view. Behaviorism holds that language learning is a process of habit formation and that there exists explicit and implicit L1 interference; mentalism believes that language learning is a hypothesis testing process, in which the learner is actively engaged. The learner will ”borrow' knowledge of his mother tongue to help his commun...