Why is language acquired？Acquiring language is probably not a simple case.The child has to acquire the categories and rules that are used at all levels of the grammar and all the rules used in conversation and discourse.There are many categories and rules，and their uses are variable.However，all normally developing children，apparently go about acquiring language with ease and success.The explanations for this have been quite varied and，also，have led to heated controversies.These controversies concern the nature of the human as a learner and，therefore，are not limited to the question of language acquisition.As has been mentioned earlier in the present dissertation，psychology directs our attention to the individual person，first as a language user and second as a language learner.And since language teaching is concerned with the acquisition by individuals of a dual language command，its theory is bound to operate with linguistic and psychological concepts of language use and language learning.Psychological thinking on these topics forms an essential part of any language teaching theory.So in this part，psychology will be dealt with，behaviorism and mentalism which were in the domain of psychology will be fully discussed.Discussion of these will serve as the theoretical bases for the discussion of the G-T Method.