Most of us have no idea what’s going on inside our heads. Yet brain scientists have uncovered details every business leader, parent, and teacher should know—like the need for physical activity to get your brain working its best. How do we learn? What exactly do sleep and stress do to our brains? Why is multitasking a myth? Why is it so easy to forget—and so important to repeat new knowledge? Is it true that men and women have different brains?
In Brain Rules, Dr John Medina, a molecular biologist, shares his lifelong interest in how the brain sciences might influence the way we teach our children and the way we work. In each chapter, he describes a brain rule—what scientists know about how our brains work—and then offers transformative ideas for our daily lives.
Medina’s fascinating stories and infectious humor bring life into brain science:
- You’ll learn why Michael Jordan was no good at baseball.
- You’ll peer over a surgeon’s shoulder as he proves that most of us have a Jennifer Aniston neuron.
- You’ll meet a boy who has a fantastic memory of music but can’t tie his shoes.
You will discover how:
- Every brain is wired differently
- Exercise improves cognition
- We are designed never to stop learning and exploring
- Memories are volatile
- Sleep is powerfully linked with the ability to learn
- Vision trumps all of the other senses
- Stress changes the way we learn
Ultimately, you’ll understand how your brain works—and how to get the most out of it.
Exercise boosts brain power.
Our brains were built for walking—12 miles a day! To improve your thinking skills, move. Exercise gets blood to your brain, bringing glucose for energy and oxygen to soak up the toxic electrons left over. It also stimulates the protein that keeps neurons connecting. Aerobic exercise just twice a week halves your risk of dementia.
The human brain evolved under conditions of almost constant motion. From this, one might predict that the optimal environment for processing information would include motion. That is precisely what one finds. Indeed, the best business meeting would have everyone walking about 1.8 miles per hour.
Researchers studied two elderly populations that had led different lifestyles, one passive and one active.
Cognitive scores were profoundly influenced. Exercise positively affected executive function, spatial tasks, reaction times, and quantitative skills.
So researchers asked: Will their cognitive scores increase if the sedentary populations become active? Yes, it turns out, if the exercise is aerobic. In four months, executive functions vastly improve; longer and memory scores also improve.
Exercise improves cognition for two reasons:
First, exercise increases oxygen flow into the brain, which reduces brain-bound free radicals. One of the most exciting findings of the past few decades is that an uptick always accompanies increased oxygen in mental sharpness.
Secondly, exercise acts directly on the molecular machinery of the brain itself. It increases neurons’ creation, survival, and resistance to damage and stress.
Chapter 1. The human brain evolved, too.
We don’t have one brain in our head—we have three. We started with a “lizard brain” to keep us breathing, added a brain like a cat’s, and then topped those with the thin layer of Jell-O known as the cortex—the third and most potent “human” brain.
We took over the Earth by becoming adaptable to change, coming down from the trees to the savannah when the climate changed.
Going from four legs to two to walk on the savannah freed up energy to develop a complex brain. Symbolic reasoning—the ability to perceive one thing as another— is a uniquely human talent. It may have arisen from our need to understand one another’s intentions and motivations, allowing us to coordinate within a group.
The brain is a survival organ. It is designed to solve problems related to surviving in an unstable outdoor environment and to do so in nearly constant motion (to keep you alive long enough to pass your genes on). We were not the strongest but developed the most robust brains, the key to survival.
The most robust brains survive, not the most muscular bodies. Our ability to solve problems, learn from mistakes, and create alliances with others helps us stay. We took over the world by learning to cooperate and forming teams with our neighbors.
Our ability to understand each other is our chief survival tool. Relationships helped us survive in the jungle and are critical to staying at work and school today.
If someone feels unsafe with a teacher or boss, they may not perform as well. Likewise, if a student feels misunderstood because the teacher cannot connect with how the student learns, the student may become isolated.
There is no more excellent anti-brain environment than the classroom and cubicle.
Chapter 2. Every brain is wired differently.
What you do and learn physically changes your brain’s appearance—it rewires it. In addition, the various brain regions develop at different rates in different people.
As a result, no two people’s brains store the same information in the same way in the same place. As a result, we have many ways of being intelligent, many of which don’t appear on IQ tests.
The author says that what you do and learn physically changes your brain’s appearance – it rewires it. So we used to think there were just seven categories of intelligence. But types of intelligence may number more than 7 billion — roughly the world’s population.
No two people have the same brain, not even twins. Every student’s brain, every employee’s, and every customer’s brain is wired differently.
You can either accede to it or ignore it. The current education system ignores it by having grade structures based on age. On the other hand, businesses like Amazon are catching on to mass customization (the Amazon homepage and the products you see are tailored to your recent purchases).
Regions of the brain develop at different rates in different people. The brains of school children are just as unevenly developed as their bodies. Our school system ignores the fact that every brain is wired differently. We wrongly assume every brain is the same.
Most of us have a “Jennifer Aniston” neuron (lurking in our head that is stimulated only when Jennifer Aniston is in the room).
Theory of Mind: The ability to understand the internal motivations of someone else and the ability to construct a predictable “theory of how their mind works” based on that knowledge. We try to see our entire world in terms of motivations, ascribing motivations to our pets and even to inanimate objects. The skill helps select a mate, navigating the day-to-day issues surrounding living together for parenting. We have it like no other creature. It is as close to mind reading as we are likely to get.
People with advanced Theory of Mind skills possess the essential ingredient for becoming effective communicators of information.
If someone does not feel safe with a teacher or boss, they may not be able to perform as well.
If a student feels misunderstood because the teacher cannot connect with how the student learns, the student may become isolated.
Chapter 3. We ignore boring things.
The brain’s attentional “spotlight” can focus on only one thing at a time: no multitasking. We are better at seeing patterns and abstracting an event’s meaning than recording detail. Emotional arousal helps the brain learn. Audiences check out after 10 minutes, but you can keep grabbing them back by telling narratives or creating events rich in emotion.
What we pay attention to is profoundly influenced by memory. Our previous experience predicts where we should pay attention.
Culture matters too. These differences can significantly affect how an audience perceives a presentation, whether in school or business.
We pay attention to things like emotions, threats, and sex. Regardless of who you are, the brain pays great attention to these questions: Can I eat it? Will it eat me? Can I mate with it? Will it mate with me? Have I seen it before?
The brain is not capable of multitasking. We can talk and breathe, but when it comes to higher-level tasks, we can’t do it.
Driving while talking on a cell phone is like driving drunk. The brain is a sequential processor, and large fractions of a second are consumed every time the brain switches tasks. This is why cell phone talkers are a half-second slower to hit the brakes and get in more wrecks.
Workplaces and schools encourage this type of multitasking. Walk into any office, and you’ll see people sending e-mails, answering their phones, Instant Messaging, and on MySpace — all at the same time. Research shows your error rate goes up 50%, and it takes you twice as long to do things.
When you’re always online, you’re constantly distracted. So the always online organization is the always unproductive organization.
Knowledge will not be richly encoded in the brain’s database if a teacher can’t hold a student’s interest.
Brains in wild animals are 15%-30% larger than tame, domestic counterparts. The cold, hard world forced the wild animals into constant learning mode. It is the same with humans. The more activity you do, the more complex it can become.
The brain cannot multitask. It is a myth. The brain focuses attention on concepts sequentially, one at a time. Switching takes time.
Chapter 4. Repeat to remember
The brain has many types of memory systems. One type follows four stages of processing: encoding, storing, retrieving, and forgetting.
Information coming into your brain is immediately split into fragments sent to different cortex regions for storage. Most of the events that predict whether something is learned also will be remembered to occur in the first few seconds of learning.
The more elaborately we encode a memory during its initial moments, the stronger it will be. You can improve your chances of remembering something if you reproduce the environment in which you first put it into your brain.
The human brain can only hold about seven pieces of information for less than 30 seconds! Which means your brain can only handle a 7-digit phone number.
If you want to extend the 30 seconds to a few minutes or even an hour or two, you must consistently re-expose yourself to the information. Memories are so volatile that you have to repeat them to remember them.
Improve your memory by elaborately encoding it during its initial moments. Many of us have trouble remembering names. If you need help remembering Mary at a party, it helps to repeat more information about her internally. “Mary is wearing a blue dress, and my favorite color is blue.” It may seem counterintuitive at first, but study after study shows it improves your memory.
Brain Rules in the Classroom.
In partnership with the University of Washington and Seattle Pacific University, Medina tested this Brain Rule in real classrooms of 3rd graders. They were asked to repeat their multiplication tables in the afternoons.
The classrooms in the study did significantly better than those that did not have repetition. If brain scientists get together with teachers and do research, we can eliminate the need for homework since learning would take place at school instead of the home.
The first few seconds of encoding new information are crucial in determining whether something initially perceived will be remembered.
The more elaborately we encode information at the moment of learning, the stronger the memory. When encoding is elaborate and profound, the memory that forms are much more robust than when encoding is partial and cursory.
The neural pathways initially used to process new information become the brain’s permanent pathways to store the information. (Like the college professor that made no sidewalks on the new campus. Instead, he waited to see where students would walk anyway, then later paved the paths.)
The more a learner focuses on the meaning of the processed information, the more elaborately the encoding is processed.
When trying to drive a piece of information into your brain’s memory, make sure you understand precisely what that information means. Likewise, if you are trying to drive information into someone else’s brain, ensure they know what it means.
Don’t try to memorize by rote and pray the meaning will reveal itself!
The more repetition cycles a memory experiences, the more likely it is to persist in your mind. The space between repetitions is critical for transforming temporary memories into more persistent forms.
Spaced learning is vastly superior to mass learning.
Deliberately re-expose yourself to information *more elaborately*, in fixed-spaced intervals, to make retrieval the most vivid it can be.
Learning occurs best when new information is incorporated gradually into the memory store rather than jammed in all at once.
Physically, “student” neurons must get the same information from the “teacher” neuron within 90 minutes, or their excitement will vanish. Then, the cell will reset to zero and act as if nothing happened.
The information must be repeated after some time has elapsed. For example, suppose the information is repeatedly pulsed in discretely timed intervals. In that case, the relationship between teacher and student neurons begins to change, so increasingly smaller and smaller inputs from the teacher are required to elicit more robust and muscular outputs from the student.
Forgetting allows us to prioritize events. Events are irrelevant to our survival will take up wasteful cognitive space if we assign them the same priority as those critical. So we don’t.
Every 3rd or 4th day in school would be reserved for reviewing the facts delivered in the previous 3-4 days. Previous information would be presented in a compressed fashion. Inspect notes, comparing with what the teacher was saying in the review. That would result in a greater elaboration of the information—a formalized exercise in error-checking.
Chapter 5. Remember to repeat
Most memories disappear within minutes, but those that survive the fragile period strengthen with time.
Long-term memories are formed in a two-way conversation between the hippocampus and the cortex until the hippocampus breaks the connection and the memory is fixed in the cortex— which can take years.
As a result, our brains only give us an approximate view of reality because they mix new knowledge with memories and store them together. The way to make long-term memory more reliable is to incorporate further information gradually and repeat it in timed intervals.
It takes years to consolidate a memory. Not minutes, hours, or days but years. What you learn in first grade is formed in your sophomore year in high school.
Medina’s dream school repeats what was learned, not at home but during the school day, 90-120 minutes after the initial learning. But, unfortunately, our schools are designed so that most real knowledge has to happen at home.
How do you remember better? Repeated exposure to information / in precisely timed intervals / provides the most powerful way to fix memory in the brain.
Forgetting allows us to prioritize events. But if you want to remember, remember to repeat.
Chapter 6. Sleep well, think well.
The brain is in a constant state of tension between cells and chemicals that try to put you to sleep and cells and chemicals that try to keep you awake. The neurons of your brain show vigorous rhythmical activity when you’re asleep—perhaps replaying what you learned that day.
People vary in how much sleep they need and when they prefer to get it, but the biological drive for an afternoon nap is universal. Sleep loss hurts attention, executive function, working memory, mood, quantitative skills, logical reasoning, and even motor dexterity.
When we’re asleep, the brain is not resting at all. On the contrary, it is almost unbelievably active! The reason we need to sleep is so that we can learn.
Sleep is important because we spend 1/3 of our lives doing it! Sleep loss hurts attention, executive function, working memory, mood, quantitative skills, logical reasoning, and even motor dexterity.
We still don’t know how much we need! It changes with age, gender, pregnancy, puberty, etc.
Napping is normal. Ever feel tired in the afternoon? That’s because your brain wants to take a nap. There’s a battle raging in your head between two armies. Each army is made of legions of brain cells and biochemicals –- one desperately trying to keep you awake, the other desperately trying to force you to sleep. Finally, around 3 p.m., 12 hours after your sleep’s midpoint, your brain wants to nap.
Taking a nap might make you more productive. A 26-minute nap improved NASA pilots’ performance by 34 percent in one study.
Wait to schedule important meetings at 3 p.m. It just doesn’t make sense.
Students are given a series of math problems with a shortcut that still needs to be revealed. Only 20% found the shortcut if answers had to be delivered same-day. But if asked after sleep, 60% found the shortcut. No matter how often the experiment runs, the sleep group consistently outperforms the non-sleep group by about 3 to 1.
Chapter 7. Stressed brains don’t learn the same way.
Your body’s defense system—the release of adrenaline and cortisol—is built to respond immediately to a serious but passing danger, such as a saber-toothed tiger. Chronic stress, such as hostility at home, dangerously deregulates a system built only to deal with short-term responses.
Under chronic stress, adrenaline creates scars in your blood vessels that can cause a heart attack or stroke, and cortisol damages the cells of the hippocampus, crippling your ability to learn and remember.
Individually, the worst kind of stress is the feeling that you have no control over the problem—you are helpless. Emotional stress has huge impacts across society on children’s ability to learn in school and on employees’ productivity at work.
Your brain is built to deal with stress that lasts about 30 seconds. The brain is not designed for long-term stress when you feel like you have no control.
The saber-toothed tiger ate you, or you ran away, but it was all over in less than a minute. If you have a terrible boss, the saber-toothed tiger can be at your door for years, and you begin to deregulate.
If you are in a bad marriage, the saber-toothed tiger can be in your bed for years, and the same thing occurs. You can watch the brain shrink.
Stress damages virtually every kind of cognition that exists. It impairs memory and executive function. It can hurt your motor skills. When stressed out over a long period, it disrupts your immune response. As a result, you get sicker more often. It disrupts your ability to sleep. You get depressed.
The emotional stability of the home is the single most significant predictor of academic success. So if you want your kid to get into Harvard, go home and love your spouse.
You have one brain. The same brain you have at home is the same brain you have at work or school. Therefore, the stress you are experiencing at home will affect your performance at work and vice-versa.
Chapter 8. Stimulate more of the senses.
We absorb information about an event through our senses, translate it into electrical signals (some for sight, others for sound, etc.), disperse those signals to separate parts of the brain, and then reconstruct what happened, eventually perceiving the event as a whole.
The brain relies partly on experience in deciding how to combine these signals, so two people can perceive the same event very differently.
Our senses evolved to work together—vision influencing hearing, for example—meaning that we learn best if we stimulate several purposes simultaneously. For instance, smells have an extraordinary power to bring back memories, maybe because smell signals bypass the thalamus and head straight to their destinations, which include that supervisor of emotions known as the amygdala.
Our senses work together, so it is important to stimulate them! Your head crackles with the perceptions of the whole world, sight, sound, taste, smell, touch, energetic as a frat party.
The smell is unusually effective at evoking memory. For example, if you’re tested on the details of a movie while the fragrance of popcorn is wafted into the air, you’ll remember 10-50% more.
The smell is essential to business. For example, when you walk into Starbucks, you smell coffee first. They have done several things to ensure that’s the case over the years.
The learning link.
Those in multisensory environments always do better than those in uni-sensory settings. They have more recall with better resolution that lasts longer, evident even 20 years later.
- students learn better from words and pictures than from words alone
- students learn better when corresponding words and pictures are presented simultaneously
- students learn better when corresponding words and pictures are presented near to each other rather than far from each on the page or screen
- students learn better when extraneous material is excluded rather than included
- students learn better from animation and narration than from animation and on-screen text
Chapter 9. Vision trumps all other senses.
Vision is our dominant sense, taking up half of our brain’s resources. However, what we see is only what our brain tells us we see, and it’s not 100 percent accurate.
The visual analysis we do has many steps.
First, the retina assembles photons into little movie-like information streams—the visual cortex processes these streams, some areas registering motion, others registering colour, etc.
Finally, we combine that information back together so we can see. We learn and remember best through pictures, not written or spoken words.
We are incredible at remembering pictures. Hear a piece of information, and you’ll remember 10% of it three days later. Add an image, and you’ll remember 65%.
Pictures beat text as well, partly because reading is so inefficient for us. Our brain sees words as lots of tiny pictures, and we have to identify specific features in the letters to be able to read them. That takes time.
Why is vision such a big deal to us? It could be how we’ve always apprehended major threats, food supplies, and reproductive opportunities.
Toss your PowerPoint presentations. It’s text-based (nearly 40 words per slide), with six hierarchical levels of chapters and subheads—all terms.
Professionals everywhere need to know about the incredible inefficiency of text-based information and the incredible effects of images. So burn your current PowerPoint presentations and make new ones.
Chapter 10. Male and female brains are different.
The X chromosome that males have one of and females have two of—though one acts as a backup—is a cognitive “hot spot,” carrying a considerable percentage of genes involved in brain manufacture.
Women are genetically more complex because the active X chromosomes in their cells are a mix of Moms and dads.
Men’s X chromosomes come from Mom, and their Y chromosome carries less than 100 genes, compared with about 1,500 for the X chromosome.
Men’s and women’s brains are structurally and biochemically—men have a bigger amygdala and produce serotonin faster, for example—but we don’t know if those differences have significance.
Men and women respond differently to acute stress: Women activate the left hemisphere’s amygdala and remember the emotional details. Men use the right amygdala and get the gist.
What’s different? Mental health professionals have known for years about sex-based differences in the type and severity of psychiatric disorders. Males are more severely afflicted by schizophrenia than females.
By more than 2 to 1, women are more likely to get depressed than men, a figure that shows up just after puberty and remains stable for the next 50 years. Males exhibit more antisocial behavior. Females have more anxiety. Most alcoholics and drug addicts are male. Most anorexics are female.
Men and women handle acute stress differently. When researcher Larry Cahill showed them slasher films, men fired up the amygdala in their brain’s right hemisphere, which is responsible for the gist of an event.
Their left was comparatively silent. Women lit up their left amygdale, the one responsible for details. Having a team that simultaneously understood the gist and details of a given stressful situation helped us conquer the world.
Men and women process certain emotions differently. Emotions are useful. They make the brain pay attention. These differences are a product of complex interactions between nature and nurture.
Chapter 11. We are powerful and natural explorers.
Babies are the model of how we learn—not by passive reaction to the environment but by functional testing through observation, hypothesis, experiment, and conclusion.
Specific parts of the brain allow this scientific approach. The right prefrontal cortex looks for errors in our hypothesis (“The sabertoothed tiger is not harmless”), and an adjoining region tells us to change behaviour (“Run!”).
We can recognize and imitate behavior because of “mirror neurons” scattered across the brain. Some parts of our adult brains stay as malleable as a baby’s, so we can create neurons and learn new things throughout our lives.
The desire to explore never leaves us despite the classrooms and cubicles we are stuffed into. Babies are the model of how we learn—not by passive reaction to the environment but by functional testing through observation, hypothesis, experiment, and conclusion. Babies methodically do experiments on objects, for example, to see what they will do.
Google takes to heart the power of exploration. For 20 per cent of their time, employees may go where their mind asks them to go. The proof is in the bottom line: 50% of new products, including Gmail and Google News, came from “20 percent time.”
So you get to know and learn how our mind works properly. Hope you will use this information to understand your mind and move ahead in your life.
Brain Rules Book Review
“Brain Rules” was an enlightening read, exploring the brain’s functionality from a scientific standpoint yet in an easily digestible manner. Medina brought complex neuroscience to layman’s terms, making the book accessible to everyone.
The book’s strength lies in the “12 rules,” which offer practical neuroscience applications in our daily lives. From understanding how our brains process stress to the role of sleep in memory consolidation, each rule was a fascinating dive into our brain’s workings. I particularly found the insights about exercise boosting brain power inspiring, and it’s since nudged me into regular physical activity.
However, the book can sometimes veer too much into scientific details, which may overwhelm readers looking for a quick, breezy read. This slightly detracts from its otherwise stellar narrative.
Nonetheless, “Brain Rules” is a powerful tool for anyone seeking to optimize their life based on science-backed insights into the human brain. It’s transformed my understanding of the brain, influencing how I work, rest, and play.