It's been ages since I read this, but I remember coming away with a very different impression. "Packing" is essentially storing away details in your memory. I

It's been ages since I read this, but I remember coming away with a very different impression. "Packing" is essentially storing away details in your memory. If you ever see programmers who write the solution to everything down and then are constantly looking up their notes: that's a packer. "Mapping" is essentially deriving from first principles. It frees up a lot of working memory in your head and allows you to explore the issues more freely. I think it's a bit more than that, though. Fluency in a task usually means being able to do it without undue planning. When you are speaking, you don't figure out the grammar of what you are saying. You just open your mouth and it kind of pops out. It's that kind of synthesis that's important. It's the same as play chess at a high level or especially playing go. You might not know exactly why one move is better than the other, but your fluency allows you to judge it correctly. To me, that's "mapping". "Packing" is a good strategy if you don't need to judge the value of your work. This is the answer: right or wrong. You can write it down. You can memorize it. You can produce it at the appropriate time. But you can't derive it without a lot of effort. This writing influenced my thinking a lot, but when I started to get involved with language acquisition, I started to feel that it's a bit limited. I think language/skill acquisition models are actually a better fit. However, this analogy is still useful in certain ways.