Myself having “acquired” two languages, i.e. without learning grammatical rules, and having “learned” three languages, i.e. with grammar translation method, I think I am in a position to speak a bit about how important learning of formal grammar can be in one situation, and how entirely useless and unimportant it can be in another situation. Importance of formal grammar varies for a native speaker and a non-native speaker. Native speakers of a language do not need to learn the grammar because they have the grammatical “patterns internalized” (Hartwell 205). This sounds more like a universal fact now. But for a moment, let’s think about a learner who has to learn a language with no “rich and complex interaction with the environment” (208), where only available source is a teacher with knowledge of grammatical rules.
In this situation, formal grammar is very important. I learnt English this way. (For the information of those who did not have a chance to learn a second language through grammar translation method, the first skill that the learner learns is writing, followed by reading, listening and speaking). I learnt to write single sentences, after “drills” and practice. I memorized all the available rules including “tenses.” I was taught to understand what I read through translation. Then I would practice translating from L1 to target language and vice versa. When I was able to write more, I would think in L1 and translate it in target language to put it on paper to compose paragraphs and essays. It was not as simple as it sounds. In my mind, I was not only translating but was also applying grammar rules before pouring down the words. But there came a time when this activity became less agonizing as it used to be. Now words would come comparatively more smoothly. This was the time when I had “internalized” the rules. I would not have to consciously apply the rules because after a lot of practice, they had become part of my own knowledge. Speaking fluently till this stage was still a dream. I could not speak English well even after my M.A. I only started speaking English when I started teaching English.
Crux of the story is that, native speakers and non-native speakers learn language differently. Grammar also plays different roles in both cases. I was taught rules of grammar for my National language too that I forgot after passing the exam. I have also forgotten rules of English language, because now I have internalized those rules and don’t need them anymore. For a learner like me, formal grammar has a role that no other available tool or method could play at that particular time. At the same time, there were numerous other learners who were learning with me in the same classes, with same method, are still unable to write or speak English well enough. The only justification that I can give is—they forgot the rules before internalizing them or they never internalized the rules. To answer why could they not internalize the rules is perhaps the job of a psycholinguist.
By giving my personal example, I don’t mean to say that Grammar Translation is the only method to teach a second language. My point is that it cannot simply be disregarded as a tool at all.
Role of grammar in teaching writing is entirely a different story. Again, native and non-native speakers learn to write differently. Grammar rules might still be useless for a native writer but they are still valuable for a non-native writer. As an English teacher of non-native students, I would come across many errors that were grammatical in nature and by simply recalling the rule; the students would be able to fix the errors. And now as an English teacher of native speakers, I find certain grammatical errors that can be cured if the students are made aware of the rules.