Flyvbjerg 2001. Had videos on paramedics doing CPR, some of them beginners (i.e. had just finished their training), and some of them experienced. When you show these videos to experienced paramedics, they can guess correctly that the person in the video was experienced (90% correct rate), whereas if you show them to beginners, they're just guessing (50-50 correctness rate). The interesting part is when you show the videos to teachers of paramedics. These did worse than guessing, systematically mistaking the experts for beginners and beginners for experts. This is because beginners go by-the-book, exactly the methodology the teachers taught, and the experts know when to diverge from the book, which looks like doing it wrong.

Hubert and Stuart Dreyfus have a five-grade expert scale, and completed training puts you on grade 3, a "performer", and many teachers cannot detect where you are beyond grade 3.

Charles Darwin (1809–1882) wrote down arguments against his theories.

I had […] during many years followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favorable ones. Owing to this habit, very few objections were raised against my views, which I had not at least noticed and attempted to answer.

Darwin's technique is good but primarily mental. A slipbox helps make it natural to do this. It changes the writer's incentives from finding confirming facts (as when you write an article with an argument already in mind) to an indiscriminate gathering of any relevant information regardless of what argument it will support. Developing ideas bottom-up instead of top-down lets us focus on the most insightful ideas we encounter and welcome the most surprising turns of events.

We're still selective, but no longer filter by for/against but by relevant/irrelevant. The criterion is whether something adds to a discussion in the slipbox: "an addition as well as a contradiction, the questioning of a seemingly obvious idea as well as the differentation of an argument." In fact, "dis-confirming data becomes suddenly very attractive, because it opens up more possible connections", and "the experience of how one piece of information can change the whole perspective on a problem is exciting".

• Book: How to Take Smart Notes
• Slipbox workflow
• Slipbox pitfalls
• Potential of slipboxes

Reading something we have previously read about feels like we encounter something we already know. This comfortable feeling deceives us. The test of knowledge isn't in the feeling of recognition. If we've never otherwise retrieved this thing from memory, we won't when it counts.

From Book: A Mind for Numbers:

We don’t engage in passive rereading because we are dumb or lazy. We do it because we fall prey to a cognitive illusion. When we read material over and over, the material becomes familiar and fluent, meaning it is easy for our minds to process. We then think that this easy processing is a sign that we have learned something well, even though we have not.

It gets worse the more often we're exposed to the same story, as we'll less and less feel the need to put in the effort and ask questions about it to commit it to memory for real.

Related: mere-exposure effect / Zeigarnik effect