Truth be told, I haven’t read much about current ‘language acquisition theory’, and part of why I can’t be bothered to read it (unlike some users on the forum who try to use it to refine their approach – that’s a personal choice, and I can respect their dedication) is that it simply seems like we’ve drawn almost no conclusions so far. I think such research has invalidated more things than it has validated, and so I’d much rather experiment on my own on the basis of whatever I’ve found to work for me so far. Like you said, I think each person should use the methods that work best for him/her.
I’ll try not to ramble too much, because I know I penned a fairly vehement response to a thread about the ‘input hypothesis’ and why I think it’s not sufficient to stick strictly to ‘input’ in order to learn (and so I don’t want to reproduce it here), but I’ll just say that my experience is that massive engagement with the language is more helpful: even if you’re just listening to Japanese music or reading Japanese texts, I think some attempt needs to be made to understand the material in order for the process to be efficient for learning. Letting audio run in the background or scanning a page repeatedly with your eyes will probably get some words to stick after a while, but understanding at least some of those words will aid retention. This isn’t even language acquisition theory, it’s how our memories work: it’s easier to retain something when we understand it, or when we’re able to structure our knowledge based on things we already know.
Literally the only skill I’ve found to grow without much conscious effort during immersion is listening comprehension: falling asleep with an anime episode playing for months on end let me follow the Tobira recordings without much difficulty, even when my eyes and brain couldn’t come up with the readings for the words on the page fast enough. My theory is that listening while making a bare minimum of effort to understand teaches your brain to pick apart syllables in the target language. Actually understanding the words I heard, however, required my vocabulary to expand, which did not happen automatically.
My French fluency grew fastest on the night I got lost on the Eiffel Tower: I translated back and forth between French and English in order to pretend that I was a tour guide so my friends and I wouldn’t be targeted by pickpockets who might have thought we were clueless tourists (we really were, however, and we were students, at that). That conscious effort to rapidly express myself untied my tongue, and I found myself relating the night’s events to my French host as I travelled home that evening more fluently than I ever could before.
To conclude, mass immersion while making the effort to understand will likely lead to plenty of vocabulary being acquired, but if you want to accelerate the process of becoming able to use the language fluently for expression, then you’ll have to get used to using what you’ve learnt yourself, and such practice is the sort of stuff that doesn’t (traditionally) feature in the MIA and other methods based on the ‘input hypothesis’.
(PS: I know I used ‘you’ a lot, but I’m really just addressing language learners in general. I’m not aiming this at anyone in particular.)
