Over 400,000 people visited Farnam Street last month to learn how to make better decisions, create new ideas, and avoid stupid errors. With more than 100,000 subscribers to our popular weekly digest, we've become an online intellectual hub. To learn more about we what do, start here.

What Are You Doing About It? Reaching Deep Fluency with Mental Models

The mental models approach is very intellectually appealing, almost seductive to a certain type of person. (It certainly is for us.)

The whole idea is to take the world’s greatest, most useful ideas and make them work for you!

How hard can it be?

Nearly all of the models themselves are perfectly well understandable by the average well-educated knowledge worker, including all of you reading this piece. Ideas like Bayes’ rule, multiplicative thinking, hindsight bias, or the bias from envy and jealousy, are all obviously true and part of the reality we live in.

There’s a bit of a problem we’re seeing though: People are reading the stuff, enjoying it, agreeing with it…but not taking action. It’s not becoming part of their standard repertoire.

Let’s say you followed up on Bayesian thinking after reading our post on it — you spent some time soaking in Thomas Bayes‘ great wisdom on updating your understanding of the world incrementally and probabilistically rather than changing your mind in black-and-white. Great!

But a week later, what have you done with that knowledge? How has it actually impacted your life? If the honest answer is “It hasn’t,” then haven’t you really wasted your time?

Ironically, it’s this habit of “going halfway” instead of “going all the way,” like Sisyphus constantly getting halfway up the mountain, which is the biggest waste of time!

See, the common reason why people don’t truly “follow through” with all of this stuff is that they haven’t raised their knowledge to a “deep fluency” — they’re skimming the surface. They pick up bits and pieces — some heuristics or biases here, a little physics or biology there, and then call it a day and pull up Netflix. They get a little understanding, but not that much, and certainly no doing.

The better approach, if you actually care about making changes, is to imitate Charlie Munger, Charles Darwin, and Richard Feynman, and start raising your knowledge of the Big Ideas to a deep fluency, and then figuring out systems, processes, and mental tricks to implement them in your own life.

Let’s work through an example.


Say you’re just starting to explore all the wonderful literature on heuristics and biases and come across the idea of Confirmation Bias: The idea that once we’ve landed on an idea we really like, we tend to keep looking for further data to confirm our already-held notions rather than trying to disprove our idea.

This is common, widespread, and perfectly natural. We all do it. John Kenneth Galbraith put it best:

“In the choice between changing one’s mind and proving there’s no need to do so, most people get busy on the proof.”

Now, what most people do, the ones you’re trying to outperform, is say “Great idea! Thanks Galbraith.” and then stop thinking about it.

Don’t do that!

The next step would be to push a bit further, to get beyond the sound bite: What’s the process that leads to confirmation bias? Why do I seek confirmatory information and in which contexts am I particularly susceptible? What other models are related to the confirmation bias? How do I solve the problem?

The answers are out there: They’re in Daniel Kahneman and in Charlie Munger and in Elster. They’re available by searching through Farnam Street.

The big question: How far do you go? A good question without a perfect answer. But the best test I can think of is to perform something like the Feynman technique, and to think about the chauffeur problem.

Can you explain it simply to an intelligent layperson, using vivid examples? Can you answer all the follow-ups? That’s fluency. And you must be careful not to fool yourself, because in the wise words of Feynman, “…you are the easiest person to fool.

While that’s great work, you’re not done yet. You have to make the rubber hit the road now. Something has to happen in your life and mind.

The way to do that is to come up with rules, systems, parables, and processes of your own, or to copy someone else’s that are obviously sound.

In the case of Confirmation Bias, we have two wonderful models to copy, one from each of the Charlies — Darwin, and Munger.

Darwin had rule, one we have written about before but will restate here: Make a note, immediately, if you come across a thought or idea that is contrary to something you currently believe. 

As for Munger, he implemented a rule in his own life: “I never allow myself to have an opinion on anything that I don’t know the other side’s argument better than they do.”

Now we’re getting somewhere! With the implementation of those two habits and some well-earned deep fluency, you can immediately, tomorrow, start improving the quality of your decision-making.

Sometimes when we get outside the heuristic/biases stuff, it’s less obvious how to make the “rubber hit the road” — and that will be a constant challenge for you as you take this path.

But that’s also the fun part! With every new idea and model you pick up, you also pick up the opportunity to synthesize for yourself a useful little parable to make it stick or a new habit that will help you use it. Over time, you’ll come up with hundreds of them, and people might even look to you when they’re having problems doing it themselves!

Look at Buffett and Munger — both guys are absolute machines, chock full of pithy little rules and stories they use in order to implement and recall what they’ve learned.

For example, Buffett discovered early on the manipulative psychology behind open-outcry auctions. What did he do? He made a rule to never go to one! That’s how it’s done.

Even if you can’t come up with a great rule like that, you can figure out a way to use any new model or idea you learn. It just takes some creative thinking.

Sometimes it’s just a little mental rule or story that sticks particularly well. (Recall one of the prime lessons from our series on memory: Salient, often used, well-associated, and important information sticks best.)

We did this very thing recently with Lee Kuan Yew’s Rule. What a trite way to refer to the simple idea of asking if something actually works…attributing it to a Singaporean political leader!

But that’s exactly the point. Give the thing a name and a life and, like clockwork, you’ll start recalling it. The phrase “Lee Kuan Yew’s Rule” actually appears in my head when I’m approaching some new system or ideology, and as soon as it does, I find myself backing away from ideology and towards pragmatism. Exactly as I’d hoped.

Your goal should be to create about a thousand of those little tools in your head, attached to a deep fluency in the material from which it came. 


I can hear the objection coming. Who has time for this stuff?

You do. It’s about making time for the things that really matter. And what could possibly matter more than upgrading your whole mental operating system? I solemnly promise that you’re spending way more time right now making sub-optimal decisions and trying to deal with the fallout.

If you need help learning to manage your time right this second, check out our Productivity Seminar, one that’s changed some people’s lives entirely. The central idea is to become more thoughtful and deliberate with how you spend your hours. When you start doing that, you’ll notice you do have an hour a day to spend on this Big Ideas stuff. It’s worth the 59 bucks.

If you don’t have 59 bucks, at least imitate Cal Newport and start scheduling your days and put an hour in there for “Getting better at making all of my decisions.”

Once you find that solid hour (or more), start using it in the way outlined above, and let the world’s great knowledge actually start making an impact. Just do a little every day.

What you’ll notice, over the weeks and months and years of doing this, is that your mind will really change! It has to! And with that, your life will change too. The only way to fail at improving your brain is by imitating Sisyphus, pushing the boulder halfway up, over and over.

Unless and until you really understand this, you’ll continue spinning your wheels. So here’s your call to action. Go get to it!