Book SummaryBrain Rules, by John Medina

1-Page Summary1-Page Book Summary of Brain Rules

Our brains are uniquely complex information processors, yet most people know little about how they work. When we understand how our brains have evolved to function, we can work with our brains’ natural impulses and tendencies to improve our thinking and learning in all aspects of our lives.

John Medina argues that our brains have evolved to increase our chances of survival by achieving these three core functions:

1. Solve problems.
2. Function in an unpredictable environment.
3. Operate in near-constant motion.

He takes the reader step-by-step through 12 rules that he says help fulfill these core functions. We’ve grouped these rules into five categories that correspond to recurring themes among them:

• Category 1: How Nature Makes a Brain
  • Our Brains Have Evolved for Survival (Rule 1)
  • Our Brains are Each Uniquely Wired (Rule 5)
• Category 2: How Your Environment Influences Your Brain
  • Exercise Boosts Brain Function (Rule 2)
  • We Need Sleep to Think (Rule 3)
  • Stress Can Hurt the Brain (Rule 4)
• Category 3: How a Brain Perceives Stimuli
  • Our Senses Depend on One Another (Rule 8)
  • Vision is the Dominant Sense (Rule 9)
  • We’re Wired to Respond to Music (Rule 10)
• Category 4: How a Brain Thinks, Part 1
  • Multitasking Doesn’t Work (Rule 6)
  • The Brain Needs to Form, Retrieve, and Forget Memories (Rule 7)
• Category 5: How a Brain Thinks, Part 2
  • Gender Affects Thought Processes (Rule 11)
  • We Learn By Exploring (Rule 12)

Category 1: How Nature Makes a Brain

Medina argues that our environment has shaped our brain development throughout our evolution and continues to influence the way our brain works today. He proposes two rules that underpin this theory:

• Rule 1: Our brains evolved for survival.
• Rule 5: Our brains are all wired uniquely based on our individual experiences.

Rule 1: Our Brains Have Evolved for Survival

Medina explains that our brains evolved in response to changes in both our physical bodies and our environments. Each of these influences led to the development of our unique human abilities.

When we evolved to walk on two legs instead of four, our bodies could send more energy to our brains because walking on two legs is more efficient. In addition, when we adapted to environments ranging from jungles to savannahs and beyond, our brains had to prove flexible enough to respond to the different survival pressures.

(Shortform note: Research supports Medina’s theory that walking on two legs freed up energy for brain development—recent studies show that chimpanzees use much less energy when they walk on two legs instead of four. Scientists also largely agree that our brains developed in response to environmental changes but often disagree about which changes had the most impact—some researchers believe that the most brain development occurred during highly variable climactic periods, while others think it happened more during stable periods, which were most conducive to thriving human life.)

Medina argues that in response to these influences, we developed three uniquely human characteristics:

• We can use our imaginations: Our ability to use our imaginations sets us apart from other species. Our imaginations allow us to engage in symbolic reasoning, or the ability to make meaning from things that aren’t inherently meaningful—like seeing a duck in a cloud. (Shortform note: some evidence shows that monkeys also have some ability to use symbolic reasoning, albeit to a much lesser degree than humans. This would support the theory that symbolic reasoning is a useful evolution, as other species appear to have developed it also.
• We embrace variety: Our evolutionary challenges also led to another specifically human characteristic: our acceptance of variety and change, which was necessary because early humans had to deal with great instability. (Shortform note: Some anthropologists say that our ability to accept change—including the ability to adapt to various diets—is the primary reason our species was able to spread across the globe, even above other factors like long legs or the ability to use tools.)
• We cooperate with others: Medina also notes that humans cooperate with one another far more than other species. This is because we’re not as strong as many other animals, and so we had to develop the ability to work with one another to survive. In doing so, we developed the ability to imagine what others may be thinking or feeling. Because we can “read” people’s emotions, we can communicate and solve complex problems with one another. (Shortform note: Researchers have found that some other species, such as dogs and primates, also have the ability to read emotions. Scientists postulate that all kinds of animals might evolve these abilities because cooperation can bolster the health of a species when individuals help raise each others’ offspring and form social networks.)

Rule 5: Our Brains Are Each Uniquely Wired

Medina explains that while our brains all fulfill the same basic functions, the neural structure of every brain is unique to every individual. This is why every person has an individual array of talents and skills.

Neurons are the cells that carry out the brain’s functions. They allow the brain to absorb...

Brain Rules Summary Shortform Introduction

Brain Rules was written by molecular biologist John Medina to explain 12 essential cognitive functions that shape the way we react to and interact with the world. Medina wrote the book for the vast majority of people who know little about the brain, to help them figure out how to use the brain’s natural instincts, desires, capabilities, and tendencies to improve their memory, ability to learn and solve problems, and other cognitive skills.

About the Author

John Medina is a developmental molecular biologist and an affiliate professor of bioengineering at the University of Washington School of Medicine. His research focuses on the genetics of psychiatric disorders and the genes involved with human brain development.

Connect with John Medina:

• Website
• Twitter
• Facebook

The Book’s Publication

Brain Rules was published in 2011 by Pear Press. Through that publisher, Medina has published several follow-ups to Brain Rules, including *[Brain Rules for...

Brain Rules Summary Introduction

Our brains are uniquely complex information processors, yet most people know little about how they work. By learning about core brain functions, we can improve our thinking and learning in all aspects of our lives.

Today, our lives are at odds with how our brains are designed to function. We evolved to travel throughout dangerous outdoor environments, but the sedentary lives many people now lead don’t align with how our brains function best. We also experience much more stress than we’re built to, and don’t always engage our senses to the fullest extent. Throughout Brain Rules, Medina addresses how current norms, like classrooms where children remain seated or jobs with high stress levels, work against our brains. By learning about our brain functions, we can make the most of our cognitive...

Brain Rules Summary Category 1: How Nature Makes a Brain

The first category focuses on how natural processes have shaped the brain. Medina describes two rules that fall under this category:

• Rule 1: Our brains evolved to adapt to new environments
• Rule 5: Our brains are all wired uniquely based on our individual experiences.

These two rules affect how we approach the world and allow us to learn from changes and problems in our lives.

Rule 1: Our Brains Have Evolved for Survival

For the first rule, Medina starts at the beginning of the human race.

In this chapter, Medina discusses how the physical adaptations of the human body helped our brains to develop in the advanced way that led to our species’ unique intelligence. He says that this specialized evolutionary process led to the development of three uniquely human characteristics: the ability to imagine, the ability to embrace variety, and the ability to cooperate.

By understanding the evolution of the brain and how it led to these characteristics, we can learn how brain evolution has allowed us to thrive.

Physical Adaptations Allowed for Brain Development

According to Medina, one particular advance played a major role in our brain evolution: the...

Shortform Exercise: How Do You Imagine and Cooperate?

Medina described symbolic reasoning and cooperation as two special features of human behavior. Everybody makes use of these skills in their daily lives, whether they think about it or not.

Think of a time when you were working with others, and you had to “read” someone else’s emotions or motivations to get effective work done. (For example, if you’re proposing ideas for a project with a coworker, you might have to read their emotions to assess whether they like your proposals.) What did you think that person was feeling or thinking?

Brain Rules Summary Category 2: How Your Environment Influences Your Brain

The first category described how fundamental natural processes influence the brain. In this category, Medina describes how aspects of our individual environments and lifestyles influence our brain functions. Medina writes that exercise, sleep, and stress are three key aspects of our lives which affect our cognition, brain health, and learning.

Rule 2: Exercise Boosts Brain Function

Medina argues that our brain function is highly influenced by whether or not we exercise, and that more exercise results in more brain power. He explores why we've evolved to exercise frequently, how exercise benefits our brains, and how sedentary lifestyles harm them. He then describes several important truths that illustrate exercise’s importance.

Our Bodies Want to Exercise

According to Medina, our ability and desire to exercise are baked into our biology. As we’ve mentioned before, humans had to contend with intense environmental conditions, and constant motion was necessary for survival. For example, when early humans migrated from shrinking rainforests into vast, dry savannahs, they had to walk and run long distances to find food and shelter and to fend off hostile...

Shortform Exercise: How do You Address Stress?

Everyone experiences stress in their life sometimes. Now that you have some more knowledge about the causes and effects of stress, think about what you do when you experience stress.

Reflect on a time when you experienced chronic stress. For example, you could have been falling behind on deadlines at work, or you could have been in the middle of a difficult conflict with a loved one. How did this stress affect you, mentally and physically?

Brain Rules Summary Category 3: How a Brain Perceives Stimuli

The previous category focused on how our brains respond to our environments. This category focuses on the brain’s perception of sensory information. Medina writes that we learn best when we use more than one sense, that vision is the most important sense, and that we’re hardwired to respond to music. According to Medina, understanding our responses to sensory stimuli helps our learning, work performance, and happiness.

Rule 8: We Learn Best When Using Multiple Senses

In this chapter, Medina contends that, because we evolved to live in a multi-sensory world, using more than one sense at once improves our learning. He describes how we take in sensory information, why our senses improve when we combine them, and how using multiple senses benefits learning specifically. He also shares ideas for incorporating multi-sensory learning into your life.

Sensing, Routing, and Perceiving

When we process sensory information, our brains take us through three steps: sensing, routing, and perceiving. These steps allow us to take disparate sensory information and combine it into a logical whole.

**The first step is sensing, or the absorbing of sensory input....

Shortform Exercise: How Do You Use Visual Aids?

Because vision is the most dominant sense, visual aids can help us learn new information.

Describe a time when a visual aid helped you learn or remember information. For example, maybe a documentary helped you remember a historic event, or images in a presentation at work helped you learn a new concept.

Brain Rules Summary Category 4: How a Brain Thinks, Part 1

The previous category focused on how the brain integrates sensory information. This category focuses on a more conscious process: thinking. Medina argues we can improve our learning and performance by understanding how the brain’s thought processes work. This category discusses how the brain pays attention and how the brain creates and retrieves memories.

Rule 6: Paying Attention Is a Multi-Step Process

Medina argues that the better we’re able to focus on something, the better we’re able to learn it and remember it. In this chapter, he explores how we pay attention, what piques our attention, and why multitasking doesn’t work.

How Attention Works

At any given time, there are millions of sensory neurons carrying messages to your brain, each competing for your attention. But only a few capture it. Stimuli direct our attention and help us to determine what is most important to focus on at any given moment. If our brains didn’t direct our attention to specific stimuli, so many things would be competing for our attention that it’d be difficult to focus on any one.

To pay attention, our brains go through a process controlled by three neural networks, which are...

Shortform Exercise: How Do You Use Your Memory?

Medina argues that we can strengthen our memories through repetition. A few of the techniques Medina suggests include repeating information over an extended period of time, giving meaning to information, reflecting on and discussing information soon after you learn it, and putting yourself in the same situation as when you first learned the information.

Think of a time when you used one of the strategies Medina recommends, such as playing scales every day when learning to play an instrument (repetition), or creating acronyms when studying for a test (making meaning). How effective was the strategy?

Brain Rules Summary Category 5: How a Brain Thinks, Part 2

In the previous category, Medina described some of the brain’s fundamental cognitive processes. In this category, Medina describes two more aspects of our lives that influence our thinking and learning: gender and exploration.

Rule 11: Gender Affects Thought Processes

In this chapter, Medina discusses factors with more contested effects on the brain: sex and gender. Medina discusses evidence of differences in brain structure, behavior, and cognitive differences between men and women. He argues that, though more research is needed, gender affects how we think, learn, and interact with others.

(Shortform note: Since the publication of Brain Rules, science has shown much more evidence that male and female brains aren’t notably different, and that behavioral and cognitive differences between men and women are primarily influenced by social expectations. Examples will be included throughout the chapter guide to provide more context on Medina’s findings.)

Physical Differences in Male and Female Brains

Medina notes that there are observable differences in the brains of men and women. For example, various regions of male and female brains have different...

Shortform Exercise: How Do You Learn?

Medina believes that people naturally love to learn, and that people can continue learning well into their adult lives.

What’s an interest of yours you’d like to learn more about? This can be a topic you want to learn about, like U.S. history or jazz music, or a new hobby or skill you want to pursue, like playing tennis or taking a dance class.