Brain Rules Summary

Why read this

  • You’d like to know interesting insights about how the brain works, and practical applications;
  • You’re interested in improving your learning and memory abilities.

Why listen to the author

  • Medina is a developmental molecular biologist with special research interests in the isolation and characterization of genes involved in human brain development and the genetics of psychiatric disorders;
  • Has spent most of his career life working with industries dealing with mental health.



Reading time: ~8min.


Move, Exercise

Medina starts by talking about how we’re wired to be moving. How our brain was made to be on a moving body. He then gives the example of a famous bodybuilder in his 70s that was very strong. He was not only physically but also mentally strong, alert, quick-minded and intelligent [anecdotal evidence, but ok…].

Is there one factor that predicts how well one ages? He compares between two men of the same age (in their 80s). One is your typical waiting-to-die in a home for the elderly with vacant eyes just staring around. The other is a famous architect, lucid and quick minded. He asks “How can two people of the same age, age so differently?” The one factor is sedentary life. If you don’t live a sedentary life you’re more likely to age well and retain your mental strength.

He then showed that people that perform physical exercise throughout life perform better in tests made to assess long term memory, reasoning, attention and problem solving. He also showed how sedentary people’s scores would improve for a while after doing exercise but returned to their normal lower levels when they stopped and went back to being sedentary again. Being physically active also cuts by more than half the risk of getting mental disorders.

Medina then mentions that exercise stimulates our body to produce substances that promote the development of new capillaries which improve blood circulation. Fresh oxygenated blood is needed to infuse oxygen not only for the cells to breathe but also for them to let go of harmful free electrons which will attach themselves to the oxygen. As the human body is used to walking 15 km per day, so including exercise in our lives will not make us smarter but normal. Exercising will bring us to our natural state.

He says exercising is as close to a magic bullet of medicine and of staying healthy as we can get. Many companies are in fact incorporating exercise in their offices which ends up raising the performance of all their employees.

Learning Changes the Physical Structure of Your Brain

The subject switches to biology. Medina argues that whenever we learn something, physical changes occur in our brains. New connections between neurons are formed, neurons increase in diameter. A scientist once compared the brains of birds that had been taught to do tricks to ones that hadn’t. The ones that had learned the tricks had larger brains and with different folds in certain areas than the others. Violinists also have over-developed, enlarged and swollen brain zones that concern their left hand while the part that controls the right hand looks anorexic. The brain seems to act exactly like a muscle. The more activity it does the (physically) larger and more complex it becomes.

Medina then mentions that there have been studies showing that there are neurons that only fire for one specific thing. You have a neuron that only fires for a specific person you know. For example you have Jennifer Aniston neuron.

He then talks about a very good surgeon that needed to remove some bad cerebral cells from a patient. He would touch the exposed brain and the patient would tell him what he felt. The surgeon then put a piece of paper in the places where he touched so that he knew about what was each area of the brain of that particular patient. For example, for bilingual patients he had to put two papers about languages, one for each. So before watching a funny cat video, do you really want your brain to physically change itself in order to accommodate the memory of it?

He then talks about a gifted education researcher, John Bransford. Bransford says that if you want to learn something don’t start with the details but with the key ideas and in hierarchical fashion for the concepts around these larger notions to form.

There’s No Such Thing as Multitasking

It is physically impossible for you brain to multi-task. Every time we think about something else other than what we were just doing our brain has to switch the active connections. People that appear to be good at multitasking actually have good working memory and are better at doing many things sequentially. The thing is, studies show that people that are interrupted take, on average, 50% longer to accomplish tasks and make 50% more errors. It’s the “where was I?” factor. Switching tasks takes some tenths of a second. Think about how much that is. Specially while driving, studies have shown that fiddling with your phone is like being drunk.

How to Win Teacher of the Year Prize

What does John Medina do in his classes that is so special to have won this award? Well, he applies what he’s wrote in this book. Here’s the recipe:

  • Divide the class in 10 min. segments where 1 of them is explaining a general concept . The other 9 are devoted to explain details.
  • Always do it hierarchically. General idea first that’s how the brain likes it. It is important to remind often where we are. If the instructor doesn’t sprinkle where they are in terms of framework the audience has to multi-task and guess or figure out where the concepts fit in the general scope of things.
  • Explain the links between the stuff you’re teaching clearly and repetitively.
  • Then reserve every 3rd or 4th day for reviewing the facts delivered in the previous 3-4 days. Present previous information in compressed fashion. The students should inspect notes, comparing with what the teacher is saying in the review.

This one he didn’t do, because the school wouldn’t allow, but in fact Medina’s ideal school would be one where after 1h30 – 2h of teaching new stuff, teachers would review everything that was learned during that time.

How to Memorize Better

Create a Strong Memory from the Start

The book then switches focus to memorization. The stronger we encode information at the moment of learning the stronger the memory. Medina shows a test that we can do with a group of friends and whose results have been replicated throughout laboratories in the world. Give a list of ~10 words and ask one group to count the number of letters that have diagonals in them and the other to think about how they like each word. The 2nd group will remember 2 to 3 times more words than the 1st.

When trying to recall something your odds of success increase if you replicate the conditions you were in when you first learned/memorized the thing.

To add to that, the more pathways you have leading to an information the easier it is for it to be recalled. For example when learning a new word, read several examples of it, and think of its meaning for you personally.

The first few impressions of new information are crucial in determining whether it will be remembered because the neural pathways that are created to process new information end up becoming the permanent pathways the brain reuses to store the information. (Like the college professor that made no sidewalks in the new campus. He waited to see where students would walk anyway, then later paved the paths.)

Use Spaced Repetition

Scientist Robert Wagner tested mass repetition vs spaced repetition and saw that the people he experimented on recalled more if the same information had been remembered at spaced intervals instead of cramming. He also mentions the work by Ebbinghaus which endorses this idea. So, in order to better memorize things we should deliberately re-expose ourselves and in an elaborate and personal way relating it to other things.

Spaced Doing makes sense. It is a way of the brain knowing what to forget and what not to forget. Why should our brains remember something that didn’t elicit a strong emotional response (which means it isn’t dangerous, it isn’t fun, it isn’t sexy, … so basically it’s – boring) and that we didn’t use never again? It makes sense to forget that. Forget useless boring memories. But not even if something is emotionally boring, but you do it all the time, your lizard brain may not understand why it’s important, but the fact that do use it all the time means, at least, that it’s something that needs to be easily accessible.

This forgetting is stronger at the start, when the memory is still fresh. This appears to be because the electric isolating material that forms with time around the neuron and neural pathways (myelin) is still very thin as is the neural pathway itself, so it doesn’t take much for the signal and the neural pathway to disappear.

There are several studies that mention how napping improves the rest of your day’s cognitive abilities, in fact, our bodies seem to have been made for a night’s sleep and a nap during the mid-afternoon.

Rest On It

Apparently, we learn while sleeping. During night, the brain makes new connections. An experiment was conducted where students were given some math problems and a method to solve them. There was a shortcut to solving those problems, which they weren’t told. If they allowed the students to sleep during the time allowed to solve the problems, they would have triple the chance of finding the shortcut (from 20% to 60%) no matter how many times they ran the experiment.

Napping appears to have a complimentary function to night sleep, and in fact, our bodies seem to be pre-programmed for that, hence the typicall after-lunch drowsiness. In one study, a 26-minute nap improved NASA pilots’ performance by 34 percent.

Use Pictures

The next topic is about the Pictorial Superiority Effect (PSE). Memorizing information through a picture is several times more efficient than memorizing it through text. We’re talking triple or quadruple the efficiency — that is you remember more and for longer if information is presented through a picture instead of text. This effect is truly Olympian. Scientists did some tests and found that people could remember more than 2500 pictures days later after memorizing with 90% accuracy. Several tests corroborate this.

As for text and oral information, people only remember 10% of information for ~72h. One reason that may explain why text memorization is so low is that text is nothing more than a lot of pictures with minute details. For our eyes there aren’t words. Everything is a picture. Letters are just a specific type of picture that we recognize and that together with other of the same pictures, create meaning. The PSE is an established fact for many types of topics but it is unclear if some like arts, philosophy are better conveyed through narrative for example.

Hear a piece of information, and three days later you’ll remember 10% of it. Add a picture and you’ll remember 65%.

Use Your Senses

He proceeds taking about how we have evolved to use multiple senses in combination to better make sense of the world. He gives the example of a scientist who made a study where there were 3 groups of people. One was given info delivered via one sense (e.g. visually) the other by another sense (e.g. hearing) and the other with a combination of those. The 3rd group would always have better recall, memory consolidation, and problem solving capabilities. There’s a neurological phenomenon called synaesthesia in which stimulation of one sensory leads to automatic, involuntary experiences in a second sensory. People who report a lifelong history of such experiences are known as synesthetes. These generally display advanced memory.

If you’re not a synesthetes though, there’s hope. Smell seems to be great for normal people to remember emotions. It increases recall up to 50% as shown in some studies. For example, in one study they put two groups in the movie eating popcorn. Then they were asked a series of questions. However in one group they put the smell of popcorn in the room. That group was able to recall double the one without the popcorn smell. If you want to forever imprint a summer’s love into your memory use one kind of perfume every day during that period. Later on when you smell that perfume memories will come flooding. One reason for this is that smell directly stimulates the amygdala, which directly controls emotions. Smells control emotions.


The last subject of the books is stress. How chronic stress makes the immune system weaker. In a study, one group of people with happy memories and another with sad, had their blood monitored. The sad group had a weaker immune system. Stressed people are many times more likely to get a cold and other diseases.

Stressed brains learn worse than relaxed brains. He gives the example of children who have to endure their parents’ fights and arguments. Those kids, studies have shown, have higher blood pressure, more stress hormones in the urine. He says how they feel and are in fact powerless to stop the conflict and that this loss of control is emotionally crippling. The feeling of powerlessness is very stressful. Teachers find many children emotionally distracted, so upset and preoccupied by the explosive drama of their family lives that they are unable to concentrate on such mundane matters as multiplication tables.

The emotional stability of the home is the single greatest predictor of academic success.

All the best stress management books touch the same point: the biggest part of successful stress management involves getting control back into your life. See when and in what situations you feel the most helpless and tackle that.

 Key takeaways

  • Move, exercise, be physically active – it’s the best health magic pill there currently is, and it also improves your ability to learn and to keep your brain in good health to function properly in general and to resist aging better. Mix aerobic with non-aerobic, both help the body in different ways;
  • The brain is like a muscle. New information takes a physical form in your brain. The more developed you are in an area, the bigger that part of your brain becomes;
  • There’s no such thing as multitasking, only sequential activities. Each time you switch activities, your brain takes a few tenths of a second to reengage, and this re engagement increases likelihood of mistakes happening (texting and driving is very bad for this reason);
  • When learning, start from the general ideas and only then the details. As you progress in your learning, keep reviewing where you are, and how what you’re studying fits in the grand scheme of things;
  • To remember better:
    • Use spaced repetition (do things you’re trying to learn not jammed into sessions but spaced in time, trying to improve in each one);
    • Sleep on it (sleep while thinking about a problem you want to solve);
    • Prefer pictures rather than text or voice. Ideally all of them (use graphs, drawings and pics to explain stuff);
    • Use smells to elicit strong emotions (e.g. the smell of someone or a pet you loved that is no longer with you is the strongest emotional reaction you can get);
  • The feeling of powerlessness is one of the most stressful feelings one can have. Be sure not to cause others to feel that way. You’ll also be making their immune system stronger.

An interesting source made by John Medina himself with further visual and cool explanations and exercises related to this topic and the link to another summary of this book also made by him and another by Derek Sivers.

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