Can you really 'learn' the grammatical system of a foreign language?
True: Of course you can explicitly learn and memorize the rules of a particular grammatical feature and then reproduce it in a grammar test. If that is what you understand by learning the grammar of a foreign language, then it is not a myth.
Not True: However, if you want to be able to use the grammar of a foreign language proficiently, i.e. use it correctly and spontaneously in speaking, listening, reading and writing, then it is a myth. Explicit grammar knowledge or instruction is not going to help you to get better in using the grammatical features of a language. I don’t know of any research study that proves that it actually benefits the language learner. On the contrary, the findings from the research show that the way we think grammar is learned and how it should be taught is based on assumptions, not on actual evidence.
If you are more interested in the theory, have a look at the following research articles / studies:
If you are interested what this means in more practical terms for you as a learner, you might find the following resources helpful:
And last but not least my blog entry about this topic: