On Miller's Law

[holland]

Also called the 7+-2 Rule or the Magic Number 7, Miller's Law describes how many top-level ideas the human mind can hold at one time in its working memory. The working memory is what we use to solve immediate problems and complete hands-on tasks, such as creating art (!), and the strain we put on that memory when doing so is referred to as "cognitive load."

Whenever we need to traverse a flat list of concepts, Miller's Law theorizes that the most items from the list we can hold in our working memory at one time is somewhere between 5 and 9 depending on the individual. (Hence 7+-2.) However, the average number of items people can hold has gone down since Miller's studies were initially conducted, with some research claiming it's lowered to only 4 items today, likely due to reduced cognitive activity in the age of convenience.

I usually default this to 6 items on average for someone who is actively studying a skill.

However, this doesn't mean you can literally only think of 6 tiny little things. It's instead referring to chunks or symbols in our memory.

For example, when I tell you to think of an apple, you don't need to think of some vivid atom-by-atom memory of an apple you once saw. Your brain has already assigned "apple" to a single concept. Behind-the-scenes, that concept is made up of lots of other symbols, sure -- like the colors red and green, the shape of a heart, the size of a hand, the letters a-p-l-e... But those concepts aren't taking up immediate space in your memory, because they are nestled under the established concept of "apple." These subtopics are only summoned to the conscious when they are explicitly needed for something.

So as you study things and develop clear structures around them, they gradually come to take up less and less working memory (and thus induce less cognitive load), because they become mere subtopics under a more grand idea. This is called "chunking." Chunking is an often invisible process that results in us gradually thinking of what we learn about in increasingly simplified and abstract ways, as we "forget about" the smaller ideas and prerequisite skills underlying them.

But the goal of chunking isn't always to forget every subtopic. Even with lots of study and skill, we often need to consciously think of more than 6 ideas at a time. But if we can sort these practical topics in a way that lets us think through their children without losing our place in the higher-level list, we can traverse a whole field of study without a significant increase in cognitive load.

This is where the 6x6x6 Rule comes into play, in which we try to organize practical skills into sets of six no more than three layers deep.