Mental Models: How to Train Your Brain to Think in New Ways

I remember the moment I first learned what a mental model was and how useful the right one could be. It happened while I was reading a story about Richard Feynman, the famous physicist.

Feynman received his undergraduate degree from MIT and his Ph.D. from Princeton. And during that time, he developed a reputation for waltzing into the math department and solving problems that the brilliant Ph.D. students couldn’t solve.

When people asked how he did it, Feynman claimed that his secret weapon was not his intelligence, but rather a strategy he learned in high school. According to Feynman, his high school physics teacher asked him to stay after class one day and gave him a challenge.

“Feynman,” the teacher said, “you talk too much and you make too much noise. I know why. You’re bored. So I’m going to give you a book. You go up there in the back, in the corner, and study this book, and when you know everything that’s in this book, you can talk again.” 1

So each day, Feynman would hide in the back of the classroom and study the book—Advanced Calculus by Woods—while the rest of the class continued with their regular lessons. And it was while studying this old calculus textbook that Feynman began to develop his own set of mental models.

“That book showed how to differentiate parameters under the integral sign,” Feynman wrote. “It turns out that’s not taught very much in the universities; they don’t emphasize it. But I caught on how to use that method, and I used that one damn tool again and again. So because I was self-taught using that book, I had peculiar methods of doing integrals.”

“The result was, when the guys at MIT or Princeton had trouble doing a certain integral, it was because they couldn’t do it with the standard methods they had learned in school. If it was a contour integration, they would have found it; if it was a simple series expansion, they would have found it. Then I come along and try differentiating under the integral sign, and often it worked. So I got a great reputation for doing integrals, only because my box of tools was different from everybody else’s, and they had tried all their tools on it before giving the problem to me.” 2

The moment I read this story was the moment I realized that the smartest people are not necessarily the ones with the greatest raw intelligence, but often the ones with the best mental models.

What is a mental model? Let me explain.

[image error]Richard Feynman (Image Source: California Institute of Technology)
What is a Mental Model?

A mental model is an explanation of how something works. It is a concept, framework, or worldview that you carry around in your mind. Mental models guide your perception and behavior. They are the thinking tools that you use to understand life, make decisions, and solve problems.

For example, supply and demand is a mental model that helps you understand how the economy works. Game theory is a mental model that helps you understand how relationships and trust work. Entropy is a mental model that helps you understand how disorder and decay work.

Mental models are imperfect, but useful. For example, there is no single mental model from physics or engineering that provides a flawless explanation of the entire universe, but the best mental models from those disciplines have allowed us to build bridges and roads, develop new technologies, and even travel to outer space. As historian Yuval Noah Harari puts it, “Scientists generally agree that no theory is 100 percent correct. Thus, the real test of knowledge is not truth, but utility.”

The best mental models are the ideas with the most utility. Understanding them will help you make wiser choices and take better actions. This is why developing a broad base of mental models is a crucial task for anyone interested in thinking clearly, rationally, and effectively.

The Secret to Great Thinking

If a certain worldview dominates your thinking, then you’ll try to explain every problem you face through that worldview. As the common proverb says, “If all you have is a hammer, everything looks like a nail.” 3

This is something experts need to work on just as much as novices. The more you master a single mental model, the more likely it becomes that this mental model will be your downfall because you’ll start applying it indiscriminately to every problem. What starts as expertise can become a limitation.

Consider this example from biologist Robert Sapolsky. He asks, “Why did the chicken cross the road?” Then, he provides answers from different experts.

Well, if you ask an evolutionary biologist, they might say, “The chicken crossed the road because they saw a potential mate on the other side.”
If you ask a kinesiologist, they might say, “The chicken crossed the road because the muscles in the chickens leg contracted and pulled the leg bone forward during each step.”
If you ask a neuroscientist, they might say, “The chicken crossed the road because the neurons in the chicken’s brain fired and triggered the movement.”

We all have our favorite mental models, the ones we naturally default to as an explanation. Typically, we favor the concepts we are familiar with, but each individual mental model is just one view of reality. The challenges and situations we face in life cannot be entirely explained by one field or industry.

All perspectives hold some truth. None of them contain the complete truth. Thus, the secret to great thinking is to employ a variety of mental models.

The Pursuit of Liquid Knowledge

The process of accumulating additional mental models is somewhat like your vision. Each eye can see something on its own. But if you cover one of them, you lose half of the scene. It’s impossible to see the full picture when you’re only looking through one eye.

Similarly, mental models provide an internal picture of how the world works. And we should be constantly upgrading and improving the quality of this picture. The mind's eye needs a variety of mental models to piece together a complete picture of how the world works.

For this reason, it is often the combination of mental models that leads to great thinking. The more sources you have to draw upon, the clearer your thinking becomes. As the philosopher Alain de Botton notes, “The chief enemy of good decisions is a lack of sufficient perspectives on a problem.” 4

Tools for Thinking Better

Relying on a narrow set of thinking tools is like wearing a mental straight jacket. Your cognitive range of motion is limited. And when your set of mental models is limited, so is your potential for finding a solution. In order to unleash your full potential, you have to collect a range of mental models. You have to build out your toolbox.

In school, we tend to separate knowledge into different silos—biology, economics, history, physics, philosophy. But in the real world, information is not divided into neatly defined categories. In the words of Charlie Munger, “All the wisdom of the world is not to be found in one little academic department.” 5

World-class thinkers are often silo-free thinkers. They avoid looking at life through the lens of one subject. By mastering the fundamentals of many disciplines they are able to make connections and identify solutions that most people overlook. They develop “liquid knowledge” that flows easily from one topic to the next.

How to Develop Better Mental Models

Here's the good news:

You don't need to master every detail of every subject to become a world-class thinker. Of all the ideas humankind has generated throughout history, there are just a few dozen that you need to master to have a firm grasp of how the world works and upgrade your thinking.

To quote Charlie Munger again, “80 or 90 important models will carry about 90% of the freight in making you a worldly-wise person. And, of those, only a mere handful really carry very heavy freight.” 6

This article is one of the first in a series I'll be doing on mental models. I've written previously about mental models like entropy, inversion, and margin of safety and in the coming months I'll be focusing particularly on the big models that carry the heavy freight in life.

My goal is to share the most important mental models from a wide range of disciplines in a way that is easy to understand as well as meaningful and practical to the daily life of the average person. I hope you'll join the newsletter and follow along.

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Footnotes

Surely You’re Joking Mr. Feynman! by Richard Feynman. Pages 86-87.

Surely You’re Joking Mr. Feynman! by Richard Feynman. Pages 86-87.

This idea is sometimes called The Law of the Instrument or Man With a Hammer Syndrome. The original phrase comes from Abraham Kaplan's book, The Conduct of Inquiry: Methodology for Behavioral Science. On page 28 he writes, “Give a small boy a hammer, and he will find that everything he encounters needs pounding.”

One of the best ways to expand your set of mental models is to read books outside the norm. You can’t expect to see problems in a new way if you’re reading all the same things as your classmates, co-workers, or peers. So, either read books that are seldom read by the rest of your group (like Feynman did with his Calculus book) or read books that are outside your area of interest, but can overlap with it in some way. In the words of the wonderful writer Haruki Murakami, “If you only read the books that everyone else is reading, you can only think what everyone else is thinking.”

“A Lesson on Elementary, Worldly Wisdom As It Relates To Investment Management & Business” by Charles Munger. Speech at USC Business School. 1994.

“A Lesson on Elementary, Worldly Wisdom As It Relates To Investment Management & Business” by Charles Munger. Speech at USC Business School. 1994.