There are several prominent voices on the Interwebs that’ll tell you that grammar is not worth studying in foreign language learning. Now, I think what they’re getting at is that one shouldn’t be working exclusively from a textbook or grammar, but I think it’s a little misleading – you definitely do need to do some studying to master a second language quickly! Furthermore, I think there’s a real risk of ditching L1 (English) too quickly, insofar as it can be difficult to infer precise nuance in L2.
I realised recently that I can actually still follow most of what’s being said in Japanese-language anime, despite not having looked at the language for over a year. A big part of Japanese for a learner are the many verb and adjective inflections – yet I could still understand the precise meaning of each. Japanese inflections were something I’d purposefully studied in detail before, from a textbook – not great fun, but it paid off. In doing so, I’d looked at hundreds (thousands?) of English-Japanese sentence pairs – this practice meant I could understand exactly what a given construction meant.
For Cantonese however, I hadn’t (until recently) done similar study on different aspects of grammar; working out exactly what someone said took somewhat longer than just getting the gist. Additionally, I’d dropped English comparatively quickly from my study, making understanding constructions exactly difficult. So, I created a new Anki deck based on Cantonese-English sentences pairs, without Chinese characters, to try to hone the grammar points I was missing – I’ve made between 50 and 70 cards for each grammar point.
Now, this is just extra practice – I already had a good idea of what most sentences meant (new vocabulary notwithstanding) – but it’s been worth it to be completelyand immediately understand what’s being said in real life.
Why do children not seem to need this explicit clarification of grammar points? Actually, I think they do – if you watch children’s TV shows, they’ll tend to go over the same point over and over (usually ideas rather than grammar, but they repeat the same constructions anyway) – and usually with a practical demonstration. Parents will also correct children if they make mistakes; when kids go to school, they’ll also have specific tuition on the grammar of their own language.
The key ingredient here though is time. It takes a child many more years to speak grammatically in their own language than it takes a second language learner with a good method. Using a grammar and spending some time understanding sentence equivalents (between L2 and L1) is a way of shortcutting the many years of practice a child has to have to speak grammatically. Don’t spend all your time masochistically studying verb tables, but don’t write off your language’s rules as a waste of time either.