What Are Mental Models and Why Is Everyone Talking About Them?

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 was known not only for his intelligence, but also for his unusual hobbies. When he wasn't teaching physics at top universities, he played the bongos, spent years drawing nude models and making art, and developed a knack for picking the locks on safes—including one that contained top secret information about the atomic bomb. He also won the Nobel Prize in Physics in 1965.

But before all of that, 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 told 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 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

In other words, it wasn’t pure intelligence that made the difference between Feynman and his peers. It was a different set of thinking tools. Feynman wasn’t necessarily smarter than the math Ph.D. students, he just saw the problem from a new angle. By using a different equation, he got a different answer.

This 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.

Now, let me explain what a mental model is and why people seem to be talking about them in business, tech, education, and more.

richard feynman was a master of mental models
Richard Feynman (Image Source: California Institute of Technology)

What is a Mental Model?

A mental model is an explanation of how something works. Many of the most useful ideas in history are mental models. For example, supply and demand is a mental model that explains how the economy works. Game theory is a mental model that explains how relationships work. Entropy is a mental model that explains how disorder works.

Of course, some mental models are better than others. That is, some explanations of how things work are more useful than others. One of my favorite examples involves the solar system.

In the second century, a Greek mathematician named Claudius Ptolemy published a book that changed the course of history. The book claimed that the earth was at the center of the universe. According to Ptolemy, the planets and the sun revolved around the earth. We were the heart of it all.

This idea was widely adopted and became one of the most influential scientific theories of all-time. For the next 1200 years, astronomers studied the skies with the belief that the earth was at the center of everything. However, by following this assumption, astronomers were led to believe that the motion of the planets was very complicated. When they mapped out the orbit of each planet with the earth at the center, it looked like this:

Geocentric solar system model by James Ferguson 1771

Astronomers continued drawing these elaborate planetary orbits until the 1500s, when a man named Nicolaus Copernicus came along and suggested something radical. Copernicus claimed that it was actually the sun, not the earth, that was at the center of the solar system.

Once astronomers realized that the planets revolved around the sun, the complex orbit of each planet was suddenly transformed into a much simpler path. Here is the original model that Copernicus laid out in his earth-shattering book, On the Revolutions of the Heavenly Spheres:

Heliocentric solar system model by Nicolaus Copernicus 1543.

With a single idea, Copernicus brought the entire solar system into alignment. Our understanding was simultaneously deeper and more simplified. It was a perfect example of how the right mental model can clarify a situation.

Tools for Thinking Better

Mental models are the set of tools that you use to think. And it is much easier to manage the problems of life when you have the right tools. This is why developing a broad base of mental models is so crucial. If you only have one framework for thinking about the world, then you’ll try to explain every problem you face through that framework. As the common proverb says, “If all you have is a hammer, everything looks like a nail.” 3

Now, if you want to force the issue you can figure out how to use a hammer to tighten a screw—similar to how astronomers figured out how to map the motion of the planets while assuming everything revolved around the earth. But it's hard to get the optimal solution with a toolbox that is only half-full.

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.

The Secret to Great Thinking

We all have our favorite mental models, the ones we natural default to as an explanation. But each individual mental model is just one view of reality. The biologist Robert Sapolsky offers a great example of what I mean. He starts by asking, “Why did the chicken cross the road?”

Then, he begins to list possible answers different experts might give.

  • 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.”

You can look at the same situation in different ways. In everyday life, the challenges and situations we face cannot be entirely explained by one field or industry. All perspectives hold some truth about the situation, but all of them are incomplete.

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.”

This is where mental models really shine—they provide you with multiple ways of looking at the same problem. 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, the mind's eye needs a variety of mental models to piece together a complete picture of how the world works.

The Hidden Bottleneck of Innovation

If you’re smart and talented in one area, it can be easy to believe that your skill set is the answer to most problems you face. 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.

The goal is to develop “liquid knowledge”—knowledge that is silo free and flows easily from one discipline to the next. In the words of Charlie Munger, “All the wisdom of the world is not to be found in one little academic department.”

Clear thinking is less about following a checklist or trying to remember the optimal thing to do at all times. Instead, it is more about understanding how the fundamentals of one discipline lead into another.

Learn the fundamentals deeply and let them seep into every aspect of your thinking.

Brilliant people like Richard Feynman have more mental models at their disposal. This is why having a wide range of mental models is important. You can only choose the best tool for the situation if you have a full toolbox.

The best mental models not only accurately describe how things work, but also broadly apply to daily life. They improve your ability to solve everyday problems, make wiser choices, and take better actions.

How to Develop New Mental Models

In my experience, there are two good ways to build new mental models.

1. Read books outside the norm. If you read the same material as everyone else, then you’ll think in the same way as everyone else. 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 other words, look for answers in unexpected places. 4

2. Create a web of ideas that shows how seemingly unrelated ideas connect. Whenever you are reading a new book or listening to someone lecture, write down the various ways that this new information connects to information you already understand. We tend to view knowledge as separated into different silos. We think that a certain set of ideas have to do with economics and another set have to do with medicine and a third set have to do with art history. This is mostly a product of how schools teach subjects, but in the real world information is not separated like this.

mental models unrelated intersection

For example, I was watching a documentary the other day that connected the design of the Great Pyramids in Egypt with the fighting rituals of animals. According to the historians on the show, when animals are battling one another they will often rise up on their back feet to increase their height and show their dominance. Similarly, when a new Pharaoh took power in Egypt, he wanted to assert his dominance over the culture and so he built very tall structures as a symbol of power. This explanation links seemingly unrelated areas (architecture, ancient history, and animal behavior) in a way that results in a deeper understanding of the topic.

In a similar way, mental models from outside areas can reveal a deeper level of understanding about issues in your primary field of interest. 5

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

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

  3. 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.”

  4. This isn’t to say that you should avoid reading the books your peers are reading. You should probably read those too, so that you have the same baseline of knowledge.

  5. Thanks to Shane Parrish for sending me down the rabbit hole of mental models.