tldr:
I agree with nfera. I think it’s a perception for most people on LingQ.
Long winded version:
If your known word count is going up, you are not plateauing. In fact, for me, in general, my word count goes up waaaaay faster than the beginning levels. As nfera points out, if you keep on working on material with new words, or with a decent number of yellow words, then you really shouldn’t plateau in the intermediate level.
It certain does FEEL like a plateau. However, this is, in my opinion, is because, despite the higher known word count, you still often are encountering words and constructs (grammmar) that you may not truly understand yet. Also, your listening may not be keeping up as well. I think many of us using LingQ may stick to reading too much, or due to the nature of being able to easily read on LingQ anywhere, those skills may be disproportionate to listening activities. I know this is the case for me. I’ll read in line at the store, in the bathroom, while feeding the cats, in bed, etc. Listening I am doing a lot more than I used to…trying to fit in a half hour or more every day that I wasn’t before. This helps a lot, but I’m also now trying to get back to doing R+L as much as possible. It was something I had intuitively done in the beginning levels to learn the sounds and match to the words, but it was something I put to the side from about the 4000-24,000 known word stage. My thinking was that, I know how the words sound, or should sound, so I don’t really need to look at both at the same time. noxialisrex and PeterBormann put that R+L bug back in my mind. I think, despite knowing how the words, in most cases should sound…it is still way better to hear how the native pronunciation is, and especially with dialogues, be able to see what they are really trying to say as it is often shortened, abbreviated, or “blended” with the surrounding words. So one needs to keep their ear tuned and visually see. Plus it pushes the speed. If just reading you’ll tend to read slowly which isn’t helpful at all to trying to understand someone at full speed.
This intermediate stage is a LOOOOOOOOONNNNGGGG one. That’s also why it feels like a plateau. You need to learn a lot of words…and also, when it comes to listening, I was thinking…despite knowing way more words, one still may not understand a speaker. a) even if you don’t know just one word, you may lose the meaning of the sentence b) speaker may be hard to understand due to their speech (need more listening to natives practice) c) because we know many more words…but not quickly enough, I think that actually throws us off even more…because now more words we recognize, more words that we attempt to process in our heads. This ultimately freezes us. In some ways, I almost feel like I could understand people better when I didn’t know as many words. That’s truly, not the case of course, but if you can’t understand what’s being said, you can’t understand. Whether you know 5% of the words spoken or 80-90% or more.
Now, if your known word count is not going up. You need to change what you’re doing. In the intermediate stage, this shouldn’t really happen. You either need to be finding content that has new words to learn. Or your techniques are off. I’d be surprised if someone doing reading is not bumping up their known word count at a decent pace.