Is it better to go slow or fast? Is it better to acquire a language or to learn a language? Can you speed things up? Can you slow things down? If the first shall be last and the last shall be first, will the slow be fast and the fast be slow? I'd say so.
Language acquisition is a process that takes time. If you want to finish the race sooner, you have to put in more time each day. There aren't any good shortcuts. Studying and memorization seem like shortcuts but the end results only prove to slow you down.
Let's take a look at how going faster is bad and why slow and steady wins the race.
Every student of language learning would like to learn quickly. In doing so, they learn many words and grammar rules and pile on so much information that it overwhelms them. They push themselves beyond what they are ready for. They set the pace of learning but they do not get the massive amount of input and exposure to the language that is required for the brain to absorb the language. Instead, all they have is words and rules that they force themselves to think about so they can construct the language and get to the conversational level as quickly as they can.
The fast learner's model of the language in their head is incomplete. There are holes in their picture of the language which means they have holes in their head. They constantly search for the right words and ways of expressing themselves in the new language. The connections to that language in the brain are still weak because of the lack of exposure.
Whenever you learn something new, such as the name of a new person, it takes time to develop a strong connection in your brain. Whenever people can't quite remember my name, they always come up with a guess of Kevin. I think there are many more Kevins than there are Keiths. The fact that they both start with the same K sound and the same first 2 letters proves that they at least made a weak connection in their brain. If they had made a strong connection, they would have gotten my name right. If the connection was weaker, they wouldn't have even come up with the name Kevin. So there is such a thing as this connection strength.
How much more difficult it must be to make connections for a foreign language whose sounds are very different from what you are used to!
When I studied Japanese in school we used a textbook. We first learned the -masu form which is the middle of the road in terms of formality. Before I could get used to that form, then they added the dictionary form which can be used for informal situations. While I still hadn't mastered the -masu form and the dictionary form was still new to me, then the textbook added the honorific forms. Next we learned how to speak to the in-group and the out-group members which includes the humble forms of speech registers. I had so much information in my head without a chance to get used to and master any of it, is it any wonder why I couldn't speak Japanese naturally?
As Steve Kaufmann points out in his posts, the brain learns when it is ready. Read point number 2 of the post that I linked to there.
When you take a slow approach such as the TV method, you acquire the language as you go along and when you are ready. The part of the language that you have acquired will constantly get reinforced as you keep watching and listening to the language. What happens to the rest of the language that you are hearing but don't yet understand? Does it just get wasted? Is it wasted time? The answer is: NO. It is not wasted. It gets stored and your brain tries to organize it and tie it in with what it already has. When there is a new phrase or word that you keep hearing and noticing, that is because the storage is getting stronger. You are paying more attention to this new phrase because your brain is working on it.
If words you didn't understand were just discarded by your brain then you would never have learned anything because in the beginning you didn't understand anything. When you were born all you could do was hear and feel and see. You didn't come preprogrammed for English. If every word you heard was discarded because you couldn't understand it, then every time you heard a word it would be like the first time you ever heard it and you would keep discarding it. You wouldn't get anywhere.
Memory is still not completely understood by researchers. Sometimes you can't remember something. Does that mean it's gone? No. Later on you remember it. So just the simple problem of recall does not mean the memory is not there. It just means your connection or path to that memory is a little weak. You may hear something in a language you don't understand. You have no chance of recalling what was said but does that imply that your brain threw it away? If your brain threw away everything you didn't understand then you'd have no chance of learning a foreign language. So recall and storage are not the same thing. Just because you cannot recall does not mean it is not stored. I think everything gets stored. So while you are listening to language that you do not understand, it is all being stored. The more you hear it, the more important it becomes and the more your brain will work on it.
And all the while, that language which you have already acquired will get stronger and stronger. What you want is for the language to feel natural to you. If it is foreign to you then you will not be comfortable using it. So one of the benefits of natural language acquisition is that you will feel comfortable using the language. If you are like me, your recall works better when you are comfortable.
I can't tell you the exact figure but something like 80% of the words used in a spoken language are the same set of words. Whether it is 2,000 words or 5,000 words, I don't know. If most of the time you are hearing the same set of words, you are going to acquire them pretty quickly. When you acquire words, you don't have to think about them at all. When you study words, then you are constantly thinking about those words. Even after you feel you know the words quite well, you have already created a habit of thinking about them. Habits are hard to break.
But natural acquisition frees you from those habits and allows you to pass up those people who studied the language. Acquisition allows you to relax and lets your brain work more effectively. It also gives you a broader exposure to the language. While the students are studying a limited set of words, you will have heard expressions that the students never encountered before. You will be ready for it. Once you acquire the meaning you will be way ahead of those students who will be trying to recall the meaning. While the students are trying to remember the meaning, they are missing the next sentence in the conversation. You will be hearing it. They will be frustrated. You will be relaxed and getting more input that will be easily processed.
In summary, trying to go fast and forcing a pace that is not natural and that creates bad habits of thinking will only get you so far. That is the ceiling. Going at the natural pace using a natural approach is very complimentary. It relaxes you which allows your brain to work more efficiently. You only use language that you are completely comfortable with. You are not thinking about grammar or wondering if what you say sounds natural. You know it is natural and you know the grammar is correct because you've heard it a thousand times. You don't need to think about words. The words just come to you.
Even now, I've got words that just come to me. A lot of English sentences start with "You." It is natural for us English speakers to start our thoughts with "You." "You" is rarely used in Japanese. I never use "You" in Japanese. So when the Chinese word for "You" pops into my head, which it often does now, I know that the thought I was about to think was my natural tendency to use "You" to begin a sentence and because I am watching the Chinese dramas so much, it just wants to come out in Chinese. I don't have the knowledge yet to complete my thoughts in Chinese so I have to stop and then I realize that Chinese is coming to me. I didn't choose it. I didn't make a decision. It just came.
I look forward to when I've acquired enough of the language to be able to converse in it. I think it will be pleasant and feel natural which is in contrast to how I feel about Japanese.