I have personal experience with the human form of this - language learning in a vacuum.
For the last two years I've studied French every day, but only using language apps. Recently, I hired a one-on-one tutor. During lessons I find myself responding to what I think I heard with the most plausible response I can generate. Many times each session, my tutor asks me, "Do you really understand or not?" I have to stop and actually think if I do.
I don't have much multi-modal input and increasing it is challenging, but it's the best way I have to actually connect the utterances I make with reality.
For the last two years I've studied French every day, but only using language apps. Recently, I hired a one-on-one tutor. During lessons I find myself responding to what I think I heard with the most plausible response I can generate. Many times each session, my tutor asks me, "Do you really understand or not?" I have to stop and actually think if I do.
I don't have much multi-modal input and increasing it is challenging, but it's the best way I have to actually connect the utterances I make with reality.