Mental Models & Decision-Making (thinking about thinking)

Every skill this track has built so far is about doing the right things well, but this one is about picking the right things in the first place. This lesson is the toolkit: how your mind actually decides, where it reliably breaks, and the six-step check that catches it before it costs you something.

Before you start. The last lesson showed that a page you’ve re-read until it feels familiar is not one you can actually reproduce cold - that feeling of “I know this” lies to you (How to Learn (the highest-leverage skill)). This lesson is about the same lie in different clothes: feeling that a choice was good or bad, based on how it turned out, fools you exactly the same way.

The idea in 30 seconds

Your mind runs on two systems: a fast, automatic one that guesses well enough for almost everything, and a slow, deliberate one you have to consciously switch on for the choices that matter.
The fast system’s mistakes are predictable, not random: it counts money already spent that shouldn’t count anymore, and it hunts for evidence that agrees with what it already believes.
Expected value means multiplying each possible outcome by how likely it is and adding the results - the size of a win or loss, times how often it happens.
When you estimate how likely something is, start from how often things like this usually go, not from how confident this particular case feels.
A decision is good or bad because of what was known and the odds at the time, never because of how it turned out - judging it the other way teaches you the wrong lesson every time.

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