Thinking Fast & Slow: Summary Review & Takeaways

This is a summary review of Thinking Fast & Slow containing key details about the book.

What is Thinking Fast And Slow About?

Thinking Fast & Slow's main thesis is that there’s a dichotomy between two modes of thought: "System 1" is fast, instinctive, and emotional; "System 2" is slower, more deliberative, and more logical.

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The book delineates rational and non-rational motivations or triggers associated with each type of thinking process, and how they complement each other, starting with Kahneman's own research on loss aversion. From framing choices to people's tendency to replace a difficult question with one which is easy to answer, the book summarizes several decades of research to suggest that people have too much confidence in human judgment.

Who is the Author of Thinking Fast And Slow?

Daniel Kahneman is an Israeli-American psychologist notable for his work on the psychology of judgment and decision-making, as well as behavioral economics, for which he was awarded the 2002 Nobel Memorial Prize in Economic Sciences (shared with Vernon L. Smith).

What are the main summary points of Thinking Fast & Slow?

Here are some key summary points from the book:

  • We use 2 cognitive systems when thinking; they work together, but they often clash with each other.
  • System 1 makes fast instinctive judgments based on familiar patterns. It kicks in without much effort, working automatically.
  • System 2 requires focus and operates slowly and methodically with greater effort required.
  • System 1 automatically generates instinctive suggestions for System 2. If endorsed by System 2, those instinctive suggestions turn into beliefs and actions.
  • We tend to seek reasons for random events, think rare incidents more likely than they are, and tell simple stories for complex reality while making our own experiences more important than they really are.
  • We distort reality due to our “hindsight bias,” which means realigning memories and past events with new information.
  • Due to the fact that system 1 operates automatically, biases can be difficult to prevent. Since system 2 is slow and energy consuming, it’d be wise to involve it mostly when the stakes are high and when we’re about to make an important decision.
  • How a person estimates value and risks is all down to “loss aversion” and the “endowment effect.”
  • We have “2 selves” in our mind that evaluate our life experiences differently:
  • Your “experiencing self” is the one that lives your life. (System 1)
  • Your “remembering self” evaluates your experiences of life, drawing lessons from them which help shape your future. (System 2)
  • Your two systems, or selves, disprove the theory that human beings are rational (since the two systems often give conflicting thoughts).
  • The difference between the two selves means that there is happiness we experience and happiness we remember.
  • We tend to prioritize the remembering self. More often than not, it’s your remembering self that makes future decisions.
  • One way to make people believe in falsehoods is frequent repetition.
  • Using complex language when simpler language is sufficient makes you less credible.
  • Looking at the future through your past experiences can cause flawed predictions. The future is never 100% certain.
  • When faced with an extremely important but difficult question, it’d be wise to integrate and align your “two minds.”
  • Laziness is built deep into our nature. We tend to gravitate to the least demanding course of action in order to save energy.
  • We tend to overestimate how much we understand the world and to underestimate the role of chance in events and circumstances.
  • We lose touch with our intuition (System 1) when we are uncomfortable and unhappy. On the other hand, we are more prone to logical errors (System 2) when we are in a good mood.
  • We are prone to an illusion of control. We focus on what we know and neglect what we do not know, which makes us overly confident in our beliefs and predictions.
  • We underestimate the amount of time a goal or project will take. This is due to “planning fallacy”: adopting the ideal and ignoring the unknowns and the many ways things could go differently.
  • We tend to use stereotypes to shortcut our decision-making, even when those stereotypes contradict actual facts or common sense.
  • We lean toward loss aversion — the idea that losses hurt more than gains. We tend to fantasize about tiny chances of big wins (winning the lottery) and obsess about tiny chances of negative outcomes or big losses.
  • Your happiness is largely determined by what you focus on. It is determined by the meaning you give to events rather than the events themselves.

What are key takeaways from Thinking Fast & Slow?

When you’re “making sense of something,” you’re thinking about it... But with 2 cognitive systems and only 1 mind, it’s good to know which one is in charge at that moment.

System 1 is the super-fast mental processing system that handles your automatic responses (such as driving a car and turning to see where a loud noise came from) and your automatic thinking when dealing with simple statements. It’s this system that makes you react in the appropriate way whether you see a cute puppy (aww!) or something gruesome (gross!), and it reads emotions and supplies associated meanings and stereotypes. It’s the mechanical system in your brain that maintains and updates your view of your personal world, and it makes instinctive rapid decisions without having to think too hard.
Meanwhile, System 2 is the mental processing system that is used for methodical thinking. It kicks in consciously when you’re seeking formal logic and focusing on specific tasks and details, such as working out complicated math, trying new unfamiliar activities, or searching for someone in a crowd. System 2 is slower than System 1, and it thinks it’s more important because it sits in the middle of the action.
Despite spending most of our time in System 1’s neat and efficient world, it is often dismissed in favor of System 2 but really, both mental processing systems hold their own, engaging in a “division of labor” and constantly interacting with each other.

It’s easy to move from System 2 to System 1 without realizing it; this is what happens when you’re distracted or tired and can’t concentrate on a task. It’s also possible to experience both systems working at cross-purposes, as is the case when you’re presented with an optical illusion.

Takeaway #2. Strengths and Weaknesses of Both Systems

To understand which system is in use inside your mind, consider how much effort you’re exerting. If you’re walking your dog on a route you take every day and often say you could walk it with your eyes closed, you’ll be switched into System 1 (your fast system) with plenty of brainpower available for thinking while you walk. However, if you walk somewhere you don’t know or walk faster than usual on a familiar route, you’ll move into System 2, which allows you to be aware of hazards and unknowns as well as maintain the effort.

Test which system you’re in by asking yourself a math problem as you walk. If you’re in System 2, you’ll probably slow down significantly or stop walking altogether while your brain comes up with the answer. This is because System 2 (your slow system) can only cope with one intense task at a time.

Recent research has shown that when you’re in System 2, your glucose levels reduce and you’re more likely to give in to temptation, stereotype people, and only skim the surface of important issues because your cognitive energy and abilities are busy elsewhere. This can lead to selfish choices, sexist language, and superficial judgment.

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Using its “rapid associative activation,” System 1 is able to link 2 words (bread and butter, knife and fork) or a word and an image (“Summer” and an image of a beach) in your mind and create a story from scraps of information that it is presented. This can be seen in “priming”: If you are given the word “eat” and have to fill in the blank letter of S-O-_-P, your brain is going to come up with “soup” rather than “soap.” Likewise, due to the phenomenon of priming, if you see or hear the word “carrot” followed by “vomit,” your mind will connect the two instantly resulting in a physical reaction such as a grimace. Essentially, any narrative that is compelling enough will create an illusion of certainty when you’re in System 1.

It’s easy to persuade people when you appeal to System 1’s preference for simple, consistent, and memorable data. Businesses can use bold fonts, make the company or product name easy to say and therefore remember, and create rhyming slogans for their ads to appeal to shoppers.

But System 1 isn’t without flaws; since it’s in charge of assembling and maintaining your view of the world, it can easily jump to conclusions. For example, it can make you think “this is the place where all cars catch fire” if one instance of a burning car is closely followed by another similar incident,, and then you might never drive on this route again. It also clings to the first answer it comes up with, even when later information proves that the initial fast and straightforward answer was the wrong one.

Takeaway #3. Giving Meaning While Making Mistakes

System 1 likes your world to have meaning, and it does this by encouraging cause-and-effect explanations, linking things together, even when 2 pieces of information should be treated completely separately. System 1 presumes you have the whole story even when you’ve only got a tiny piece of data; this is what colors your judgment and is known as “what you see is what you get” aka WYSIATI. It fills in missing information using the “halo effect” so that you’re able to come up with a “background story” about someone based on their looks alone. (Because someone wears tie-dyed clothing, you might automatically associate them with being a new-age hippy who is a plastic-free and vegan and about to ambush you on the absurdity of single-use plastics, when in reality, that person is a doctor at a children’s hospital who wears the brightly colored clothes because it makes the sick kids smile.)

System 1 also does “anchoring”; this term is used to explain how people unconsciously tie their thinking of a certain topic to the information they’ve recently been exposed to, even when the topics are unrelated. An example could be mentioning the number 10, then asking people how many African countries belong to the United Nations. Because the number 10 is remembered, even though it’s irrelevant, it will produce lower estimates than if 65 had been mentioned before asking the question.

System 1 isn’t the only one to jump into things head first to make 2+2=500 though! System 2 magnifies your mistakes by finding reasons for you to believe them; it doesn’t dispute what System 1 presents and, instead, endorses how System 1 seeks to bring order to your world. This means that the facts that challenge your assumptions simply do not get absorbed.Our natural tendency is to focus on the content of a message rather than its relevance, so our ability to judge is impaired. Our fears and hopes for the future are based on dramatic events and images presented by the media, which make us more scared of dying in a plane crash than of heart disease or cancer. Dramatic, unlikely events act as fear anchors rather than the dull and regular threats of everyday life, so that we, as humans, make false assessments about the risks in life. And we conveniently forget that the future is unpredictable due to the ease with which we explain past events.

The “regression to the mean” is another area that we humans get muddled in. Regression to the mean discusses the theory that “over time, everything tends to return to the average.” Rather than accept this fact, we apply “causal interpretations” to random events. Let’s say that a football player has a really successful first year playing with a new team, but in his second year, he hits a slump. Rather than accept that the player was luckier in his first year than in his second, we feel the need to rationalize his decline, explaining it away by health, a relationship that took his focus away from training, or problems with teammates, the press, or fans.

Takeaway #4. Optimism or Reality?

“Narrative fallacy” describes our mind’s inclination toward the simple, physical, and explainable instead of anything unclear, abstract, or opposing. We obtain more meaning from stories that highlight characteristics such as skill or virtue, while being dismissive of luck and statistical facts, even more so when telling a story about our own life without anyone to contradict us. Further, rather than picking up on the events that didn’t happen, we focus on the few miraculous events that did occur; this is due to our “hindsight bias,” which distorts reality by realigning memories of events that have happened, so that the memories blend with new information that has been learned. When speaking of past events in our own lives, re-telling a story we are confident with, that we’ve told ourselves over and over, and that comes easily to mind, we tend to be more optimistic, more inclined to overvalue our talents compared to the talents of others, and allow our knowledge greater weight than it should have. However, ease and consistency when telling a story do not mean that the belief you hold with confidence and can happily recount word-for-word with conviction is true.

Takeaway #5. Are Any Of Us Truly Experts?

How truthfully someone accesses their own “intuition and validity” is determined by System 1.

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Some experts, just like us, play up their desirable attributes with System 1, allowing them to give quick answers to difficult questions effortlessly, which makes us believe that they know what they’re talking about, are qualified to help us, and will get guaranteed results. This is all System 1 talk, so watch out for instances of overconfident experts, especially when luck determines success more than skill, when there’s a huge gap between action and feedback, and where the challenges vary greatly. Your system 2 cannot detect the inconsistencies of their System 1.

Sadly, most of us are “loss averse” and prone to foggy thinking when it comes to making decisions about risk and value. Think about it… You probably hate losing $100 more than you like winning $150.

In addition to “loss aversion,”, we humans also tend to suffer from something called the “endowment effect.” This is when you overestimate the value of items that you do own in comparison to those that you don’t own. Take for example the property market: owners tend to think their home is worth more than it really is.

Unfortunately, industries from health to insurance know how our minds work and will use wording to get us buying what they offer. The insurance industry plays on our flawed way of thinking that rare but disastrous events such as cars being stolen and houses being burgled are more likely to happen than in reality. And this “worry factor” only goes up when we’re asked to make a decision based on the apparent likelihood of the event occurring; of course you’re going to insure everything you value when you’re bombarded with media stories of robberies! The same brain messing tactics apply to pharmaceuticals: We’re more likely to agree to being prescribed a medicine that is said to have a 0.001% risk of permanent disability than one that is said to leave 1 in 100,000 people permanently disabled, yet the statements mean exactly the same thing.

How you frame risk shapes your evaluation of it, so always be aware of how a company or expert is presenting information. Good decisions come from understanding how the information is presented to you, your own confidence in the subject (you probably accept what a doctor tells you because you haven’t been to medical school!), and the validity of the data.

Takeaway #6. Two Selves in One Mind

How often have you been conflicted over your thoughts, not knowing which thought to choose or believe? This is due to the two systems in your mind, the “experiencing self” and the “remembering self,” interacting and clashing.

The “remembering self” (slow System 2) is the part that evaluates your experiences and draws lessons from them to make “decisions” about the future. Happiness is not stored up by the remembering self, but it is affected by how the remembering self works. Since the final stages of any event gets the most weight in how you recollect the experience, the remembering self can sometimes be wrong. Examples of this remembering self are often seen in breakups, when you put more weight on the bad (or good) moments at the end than those in the beginning.

It’s the remembering self that judges whether you’re happy based on evaluating your past, with the “experiencing self” (fast System 1) getting involved in the moment-to-moment assessment of your happiness. This can cause conflict since they come from different sides of reality; the here and now and the past. It gets confusing because although System 2 creates your remembering self and your tendency to evaluate experiences based on their final moments, the bias to favor “long pleasures and short pains” comes from System 1. This can be confusing not only to you and your loved ones, but also for philosophers and policymakers, since you make different decisions about health, social, and economic matters depending on whether you’re coming from the place of System 1 or System 2.

Recognizing how the two systems work, and knowing that they don’t always act rationally, can help you to understand that “rational humans” simply do not exist and that we all need help in making better choices in all aspects of life. There should be rules in place that stop people from making mistakes due to policies that deliberately exploit the weaknesses of the mind’s 2 systems.

Takeaway #7. Helping Your Two Selves

It is difficult, yet not impossible to stop errors originating in System 1 by recognizing that your thoughts have gone into overdrive, and that you need to slow it down by asking System 2 for help. This is great for personal problems, however, is it fair that we have to sift through our 2 systems, figuring out from which side we are operating, just so that we don’t get exploited by companies?

In all areas of our lives, companies (which are run by humans with the same 2 systems, remember!) are deliberately exploiting our weaknesses due to our 2 systems. It would be far easier and better for organizations to operate on methodical rationality rather than asking us individuals to do it!

For a better life, before making any decisions, look inside yourself and see if you’re operating from System 1 or System 2. Whether you’re being sold insurance, worrying about your love life, or sitting in the doctor’s office, pause to see if you’ve been thinking fast or slow, and if you would be better off coming from your other self with this decision.

Book details

  • Print length: 499 Pages
  • Audiobook: 20 hrs and 2 mins
  • Genre: Nonfiction, Psychology, Science

What are the chapters in Thinking Fast & Slow?

Part I. Two Systems
Part II. Heuristics and Biases
Part III. Overconfidence
Part IV. Choices
Part V. Two Selves

Thinking Fast & Slow Summary Notes

Part I Summary: Two Systems

Synopsis: The primary theme of part one is a fundamental concept in cognitive psychology and decision making. By understanding the dual nature of human thinking, we can better understand the cognitive processes that underlie our behavior and action taking, and make more informed decisions in our daily lives.

Summary: Human thinking is divided into two separate systems: System 1 and System 2. System 1 is the fast, automatic, and intuitive system that is responsible for most of our everyday thoughts and actions. System 2, on the other hand, is the slow, deliberate, and effortful system that is responsible for our more complex and deliberate thinking.

Kahneman argues that our thinking is heavily influenced by System 1, which is intuitive and quick, but often prone to errors and biases. This system operates automatically and effortlessly, constantly generating rapid judgments and decisions based on past experience and current context. For example, when we see a person’s face, we immediately form a judgment about their age, gender, and emotional state, all without conscious effort.

System 2, on the other hand, is responsible for more conscious and deliberate thinking, such as solving complex problems, doing math, and resisting temptation. This system requires more effort and attention, and can quickly become fatigued. As a result, we often rely on System 1 to make decisions, even when System 2 would be more appropriate.

Kahneman’s work highlights the importance of recognizing the limitations of our intuitive thinking, and the benefits of engaging in deliberate and conscious thought. By understanding the strengths and weaknesses of each system, we can make more informed decisions, and avoid common errors and biases that are associated with relying too heavily on System 1 thinking.

Part II Summary: Heuristics and Biases

Synopsis: By recognizing the limitations of our thinking, and taking steps to overcome these biases and errors, we can make more informed and accurate decisions in our personal and professional lives.

Summary: Our thinking is often influenced by mental shortcuts or “heuristics” that we use to make quick decisions. However, these shortcuts can lead to errors and biases in our thinking.

Heuristics are useful in many situations because they allow us to make decisions quickly and with limited information. For example, if we are in a hurry, we may use the heuristic of “availability” to make a decision, which involves relying on information that is easily accessible in our memory. However, this can also lead to errors when we rely too heavily on recent or vivid information and fail to consider other important factors.

Similarly, our thinking can be influenced by biases, which are systematic errors that arise from our cognitive processes. For example, the “confirmation bias” occurs when we seek out information that confirms our existing beliefs, and ignore or dismiss information that contradicts them.

Kahneman’s work highlights the importance of recognizing these heuristics and biases in our thinking and taking steps to overcome them. This can include seeking out diverse perspectives, questioning our assumptions, and being aware of the limitations of our thinking.

Furthermore, many of the assumptions underlying traditional economic models, such as rational decision making and perfect information, do not accurately reflect how humans make decisions. Instead, our thinking is often influenced by emotions, biases, and other non-rational factors.

Part III Summary: Overconfidence

Synopsis: By recognizing our tendency towards overconfidence, and taking steps to mitigate this bias, we can make more accurate and effective decisions in our personal and professional lives.

Summary: Humans tend to be overly confident in their judgments and decisions, leading to errors and mistakes.

Overconfidence is a pervasive and persistent phenomenon, that affects people from all walks of life. This can manifest in a number of ways, such as overestimating our abilities, underestimating risks, and failing to recognize the limitations of our knowledge and understanding.

One of the key causes of overconfidence is the “illusion of validity,” which occurs when we place too much faith in our own judgments and abilities. This can lead us to be overly confident in our predictions and decisions, even when they are based on limited information or flawed reasoning.

Another cause of overconfidence is the “planning fallacy,” which occurs when we underestimate the time and resources required to complete a task. This can lead to delays, cost overruns, and other problems, as we fail to account for unexpected obstacles and challenges.

In general, Kahneman’s work on overconfidence has important implications for decision-making in a variety of fields, from finance and economics to politics and public policy. He argues that overconfidence can lead to poor decisions, increased risk-taking, and other negative outcomes and that it is important to recognize and address this phenomenon in order to make more informed and effective decisions.

What are good quotes from Thinking Fast & Slow?

“We are prone to overestimate how much we understand about the world and to underestimate the role of chance in events.”

“A reliable way to make people believe in falsehoods is frequent repetition, because familiarity is not easily distinguished from truth." (Meaning)

― Daniel Kahneman, Thinking Fast And Slow Quotes

What do critics say?

Here's what one of the prominent reviewers had to say about the book: “[Thinking, Fast and Slow] is wonderful. To anyone with the slightest interest in the workings of his own mind, it is so rich and fascinating that any summary would seem absurd.” — Michael Lewis, Vanity Fair

* The summary points above have been concluded from the book and other public sources. The editor of this summary review made every effort to maintain information accuracy, including any published quotes, chapters, or takeaways

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Chief Editor

Tal Gur is an author, founder, and impact-driven entrepreneur at heart. After trading his daily grind for a life of his own daring design, he spent a decade pursuing 100 major life goals around the globe. His journey and most recent book, The Art of Fully Living, has led him to found Elevate Society.

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