Brain Rules by John Medina [Summary]

This is a comprehensive summary of the book Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School by John Medina. Covering the key ideas and proposing practical ways for achieving what’s mentioned in the text. Written by book fanatic and online librarian Ivaylo Durmonski. Supporting Members get full access.


Our brains are marvelous machines. Yet, most of us have no idea how they actually work. This is the goal of the author, John Medina, in his book with a ridiculously long title, Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. He investigates and examines a huge pile of studies to form a 12-section guide that aims to introduce us to the main operating mechanisms of our grey matter. By doing so, professor Medina wants to expose us to better ways to process information which can potentially help us improve our lives, especially at work and school.

The Core Idea:

Once you realize what are the main needs of our brains, on an atomic level, you’ll better understand why sitting in a chair for 8 hours straight seems like an impossible feat and why we doze off in the middle of a presentation. Our brains evolved to survive in the wilderness, not in cubicles. By getting to know our fundamental desires, how our brains actually work, and what they need to thrive, we can better tackle the problems we face in the modern world.


  • Add a dose of emotion to what you’re trying to teach to make it easier for others to learn.
  • We need to expose ourselves, again and again, to important information if we want to remember it for longer.
  • Stress and the lack of control, hurts people emotionally, not only physically.

5 Key Lessons from Brain Rules:

Lesson #1: Exercise Can Boost Your Brainpower

We associate workouts with nice abs. Morning runs with a healthy lifestyle. Tabata sessions with online influencers. But there is more!

Physical exercise can also boost your brainpower.

Yes, in addition to shaping your body and fitting into last year’s jeans, regular physical activities can also improve your cognitive skills and help you become a better decision-maker.

How is this possible?

To understand this, we need to observe for a moment the requirements for human life to be preserved. Our survival requires the following three things: food, water, and fresh air. That’s basically it.

However, these three have different consequences for our bodies.

As mentioned in the book, “You can live for 30 days or so without food, and you can go for a week or so without drinking water. Your brain, however, is so active that it cannot go without oxygen for more than 5 minutes without risking serious and permanent damage.”

Or in other words, oxygen is a vital ingredient for our bodies and a couple of minutes without this precious element can cause instant death.

How is this related to physical activities?

Simple, when you move, you improve your oxygen consumption. The more and the better your consume oxygen, the better your brain operates.

The scientific explanation is rather complex and I prefer to refrain from adding even more complexity to it. But in one sentence I can say that blood flow increases when we move regularly which helps us make new blood vessels. These new blood vessels improve the overall performance of our body – including how fast and well we think.

So, workout doesn’t only improve your physical fitness, it also makes you smarter.

Besides, we have only recently started driving cars and flying to other countries. Before that, taking into account the timeline of our whole existence as a species, for the majority of our time we walked. So, if you’re not regularly moving your body, you’re preventing it from doing what it was designed to do – move.

A lifetime of exercise can result in a sometimes astonishing elevation in cognitive performance, compared with those who are sedentary.” John Medina

Lesson #2: We Have Three Brains In Our Heads

There are three brains in our heads that are layering on top of each other.

The oldest part is called the lizard brain. On top of the lizard brain, we have the mammalian brain. Lastly, on top of everything, there is the prefrontal cortex – the newest addition.

All of these intellects have different functions and responsibilities.

Here they are in short:

  • Lizard brain: In control of our basic needs – breathing, heart rate, sleeping, and waking. The lizard brain is always “conscious.” Making sure that you don’t choke to death when you’re taking a nap.
  • Mammalian brain: The functions of this part is often referred to as the “four F’s”: “fighting, feeding, fleeing, and… reproductive behavior.” This second brain is also responsible for our feelings – fear, pleasure, rage, etc.
  • Prefrontal cortex: The thing that differentiates us from animals. This part helps us fantasize, solve problems, make predictions, and also enables us to think in an abstract fashion so we can conceptualize information.

The first human was not much different from an animal. But during the years, slowly, thanks to the prefrontal cortex, the brain evolved and learned one important thing – that cooperation leads to domination.

Instead of becoming bigger, humans decided to become smarter.

After all, it’s almost impossible to conquer a wild beast all by yourself. But things rapidly improve if you find allies.

Our brains are prone to develop friendships. Not so much because we want someone to talk to, but because these relationships help us achieve more.

Suppose you are not the biggest person on the block, but you have thousands of years to become one. What do you do? If you are an animal, the most straightforward approach is becoming physically bigger, like the alpha male in a dog pack, with selection favoring muscle and bone. But there is another way to double your biomass. It’s not by creating a body but by creating an ally. If you can establish cooperative agreements with some of your neighbors, you can double your power even if you do not personally double your strength. You can dominate the world.” John Medina

Hey there, sorry to interrupt…

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