https://www.lesswrong.com/posts/bhLxWTkRc8GXunFcB/what-are-you-tracking-in-your-head
A large chunk - plausibly the majority - of real-world expertise seems to be in the form of illegible skills: skills/knowledge which are hard to transmit by direct explanation. They’re not necessarily things which a teacher would even notice enough to consider important - just background skills or knowledge which is so ingrained that it becomes invisible.
I’ve recently noticed a certain common type of illegible skill which I think might account for the majority of illegible-skill-value across a wide variety of domains.
Here are a few examples of the type of skill I have in mind: