The top sides of your ceiling fan blades are dusty because of a boundary layer effect. When the blades spin, a thin layer of air above the blades moves with the blades. That’s why the fan doesn’t throw off the dust.
A mathematical model may have very different behavior in two large regions, with a thin region of rapid transition between the two, such as the transition between the ceiling fan blade and the circulating air in the room. That transition region is called a boundary layer. In this post I want to use the term boundary layer metaphorically.
Some information you use so frequently that you memorize it without trying. And some information you use so infrequently that it’s not worth memorizing it.
There’s not much need to deliberately memorize how software tools work because that information mostly falls into one of the two categories above. Either you use the tool so often that you remember how to use it, or you use the tool so rarely that it’s best to look up how to use it just-in-time.
But there’s a thin region between these two categories: things you use often enough that it’s annoying to keep looking up how to use them, but not so often that you remember the details. In this technological boundary layer, it might be worthwhile to deliberately memorize and periodically review how things work. Maybe this takes the form of flashcards  or exercises.
This boundary layer must be kept very small. If you spend more than a few minutes a day on it, you’re probably taking on too much. YMMV.
Things may move in and out of your technological boundary layer over time. Maybe you use or review something so much that it moves into long-term memory. Or maybe you use it less often and decide to let it slip into things you look up as needed.
 Paper or electronic? In my experience, making paper flashcards helps me memorize things, even if I don’t review them. But I’ve also used the Anki software before and found it helpful.
4 thoughts on “Technological boundary layer”
Took me a moment to remember what YMMV means…
@Adi: Maybe it’s in your boundary layer.
YMMV is in my JIT have to look up region.
This Boundary Layer Effect is why we do “preflight” briefings before military missions. Much safer than assuming that everyone involved is in the Memorized Zone.
This is also a reminder that undergraduate students have a very small Memorized Zone, which is why I include a “preflight” lesson for every analysis assignment. Some of which need to be expanded; grading assignments this week reminds me that their Memorized Zone is smaller than I thought.