Complex ideas may be hard to learn in part because their components overflow working memory. But Human channel capacity increases with bits-per-chunk, and Recoding can increase chunk size. So when you’re finally able to learn something that’s eluded you, it may be because you’ve finally encoded large enough chunks (“Chunks” in human cognition) representing the constituents.
Miller suggested a narrower interpretation of this notion in his paper introducing the term (1956, p. 95):
It seems probable that even memorization can be studied in these terms. The process of memorizing may be simply the formation of chunks, or groups of items that go together, until there are few enough chunks so that we can recall all the items.
Using spaced repetition systems to see through a piece of mathematics - Michael Nielsen:
I think that what’s going on is what psychologists call chunking. People who intensively study a subject gradually start to build mental libraries of “chunks” – large-scale patterns that they recognize and use to reason. … Experts begin to think, perhaps only semi-consciously, using such chunks. The conventional representations – words or symbols in mathematics, or moves on a chessboard – are still there, but they are somehow secondary.
So, my informal pop-psychology explanation is that when I’m doing mathematics really well, in the deeply internalized state I described earlier, I’m mostly using such higher-level chunks, and that’s why it no longer seems symbolic or verbal or even visual. I’m not entirely conscious of what’s going on – it’s more a sense of just playing around a lot with the various objects, trying things out, trying to find unexpected connections. But, presumably, what’s underlying the process is these chunked patterns.
Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63(2), 81–97. https://doi.org/10.1037/h0043158 Miller - The magical number seven, plus or minus two