Thinking Fast and Slow by Daniel Kahneman [Actionable Summary]

This is a comprehensive summary of the book Thinking Fast and Slow by Daniel Kahneman. 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 and a printable version of this summary.

The Book In Three Or More Sentences:

After spending years studying and documenting biases, Daniel Kahneman and his associate Amos Tversky, ​who sadly perished before this book was published, created this masterpiece. A book teaching us valuable things about how our mind is designed to work. In particular, the type of errors our brains are prone to make when making decisions. The text will help you understand why our first reaction to a complex problem is usually not that good, but if we take the time to think, we will find better solutions. Thinking, Fast and Slow is full of examples of how we delude ourselves. And by understanding these flaws, we can prevent doing stupid things in the future.

The Core Idea:

As the title hints, there are two systems that turn the cogs in our heads. System 1 is fast, automatic, reckless, often irresponsible, but extremely effective in keeping us alive. System 2 is the opposite. It’s categorized as slow, deliberate, boring but extremely reliable when complex calculations require our attention our difficult problems arise. By showcasing the various flaws embedded in the way we think, Daniel Kahneman wants to enhance our intelligence and improve our mental stamina.

Reason To Read:

Realize that you are blind about your blindness. Often acting impulsively instead of rationally. Understand the common thinking flaws we all possess and learn how to avoid them.


  • System 1 is fast and reckless. Responsible for handling dangerous situations. System 2 is slow and deliberate. Responsible for preventing you from entering dangerous situations in the first place.
  • Our default response – our intuition – is often wrong. Sadly, we are blindly unaware of this fact. Learning about our inherent errors will make us more flexible.
  • Transforming complicated tasks into nearly effortless activities can happen when we practice and proactively seek feedback from our peers.

8 Key Lessons from Thinking Fast and Slow:

Lesson #1: There Are Two Modes of Thinking Governing Our Actions

How can you describe yourself?

Most people, identify as conscious, rational beings who have clear rules and know what they want. Carefully consider all the options before buying something. Summon logic when it’s needed. And, rarely go out of line unless there is a real need to do that.

Based on the finding in the book, you’re most probably wrong about yourself.

In most situations, we are doing things based on how we feel, not on what’s right and reasonable.

And how we feel is part of System 1 where System 2 is about adding a dose of rationality to what we’re doing.

A large portion of the book – as we can sense from the title – is dedicated to explaining what is fast thinking and what is slow thinking. But the underlying goal of the author is to present something else. He wants to showcase that although we are the most sophisticated creatures on the planet. Posses the largest brain amongst all other living things, we are mostly controlled by our fast thinking – that is, we rely heavily on intuition, not reason. As mentioned in the book, “Although System 2 believes itself to be where the action is, the automatic System 1 is the hero of the book.”

To understand the two modes of thinking, let’s see the main characteristics of our two systems:

  • Fast Thinking (System 1): This system is responsible for keeping you alive. System 1 doesn’t rely on logic. It’s mostly powered by our basic instincts – eat, survive, feel safe, feel good, reproduce. System 1 responds automatically based on our ingrained needs and habits. For example, jump when a car is approaching, sense when someone is angry, smoke when you’re nervous, read and understand simple sentences, find the answer to 2 + 2. You can imagine System 1 as a dumb caveman.
  • Slow Thinking (System 2): Our second system needs time to boost. It requires effortful concentration. We use System 2 to answer difficult questions. Here things like comparing different options, using reason, rationality, stoping yourself before you say something stupid come into play. For example, System 2 will focus on a particular task, stop while walking to consider the possible options, fill out a tax form, think about ourselves from a different perspective. You can imagine System 2 as a cigarette-smoking philosopher.

Everything we encounter first goes through System 1 for filtering. And a lot of times, we never let it pass to System 2 for examination. For example, instead of paying attention to a problem presented to us (use slow thinking), we might answer with the first thing that comes to our mind (use fast thinking).

As you can sense, this approach often leads to undesirably bad outcomes – incorrectly blame someone or say something stupid. That’s why, a lot of times, deliberately waiting so we can activate System 2 is required to reach the best answer to a question.

“I describe System 1 as effortlessly originating impressions and feelings that are the main sources of the explicit beliefs and deliberate choices of System 2. The automatic operations of System 1 generate surprisingly complex patterns of ideas, but only the slower System 2 can construct thoughts in an orderly series of steps.” Daniel Kahneman

Lesson #2: Become An Expert To Enhance Your Fast Thinking

There are two ways to ensure that the first answer you give to a difficult question (imaging that you should give an answer to 17 x 25) will be correct.

You can enhance System 1, or you can simply allow yourself more time to think – invite System 2.

A skillful mathematician who is consuming formulas for breakfast will probably solve the calculus problem above with ease – in seconds. This, however, doesn’t mean that he has a computer chip implanted in his head. This simply happens when you master a specific field. Your slow thinking becomes your fast thinking. In other words, you become an expert.

To get a better understanding of this concept. Let’s read a passage from the book: “We have all heard such stories of expert intuition: the chess master who walks past a street game and announces “White mates in three” without stopping, or the physician who makes a complex diagnosis after a single glance at a patient.”

The accurate diagnosis of a doctor or of a car mechanic without looking under the hood involves no magic. It’s based on experience. As chess masters can move quickly on the board because they’ve practiced thousands of moves, we can too, increase our operating memory and boost our intuitive judgments.


Well, it takes time. And, it requires the following simple realization: You can’t turn off System 1. Your intuition will always try to dominate reason. This means that you should often mistrust your first impressions. The first automatic answer generated by your brain. Until, at least, you’ve devoted a large portion of your life towards solving a specific set of problems. When this point is reached, you will, seemingly instantaneously, give correct answers to even difficult problems.

“The psychology of accurate intuition involves no magic. Perhaps the best short statement of it is by the great Herbert Simon, who studied chess masters and showed that after thousands of hours of practice they come to see the pieces on the board differently from the rest of us. You can feel Simon’s impatience with the mythologizing of expert intuition when he writes: ‘The situation has provided a cue; this cue has given the expert access to information stored in memory, and the information provides the answer. Intuition is nothing more and nothing less than recognition.'” Daniel Kahneman

Lesson #3: We Miscalculate Whether Events Are Good or Bad

Nature has put mankind under the power of two masters: pain and pleasure. And according to the research in the book, when we’re exposed to a short period of pain that abruptly stops, we’re more likely to remember this incident as a lot more painful if we rather experience pain over time which slowly increases or decreases.

Or in other words, duration doesn’t count when we experience pain or pleasure. The peak (best or worst moment) at the end of the experience is what actually matters to the brain.

Let me try to explain this better:

There are two selves hiding inside us: The experiencing self and the remembering self.

  • The experiencing self asks: “Does it, and how much it hurts now?”
  • The remembering self, on the other hand, asks the following: “How was the overall experience?”

We rely on those two when we make decisions with one tiny comment: The remembering self has greater power when we’re making future decisions.

Even though the average length of fixing a tooth is less than 5 minutes, we remember a visit to the dentist as the worst thing in our lives. Why? Because, for a short period of time, we experience a large portion of targeted pain.

This short additional example will give you a better perspective on how we remember things: A man was listening to a long symphony recorded on a disc, however, there was a scratch at the end of the disk and the end result was a shocking sound. After being interviewed, the man mentioned that the bad ending destroyed the whole experience. But if we look at this objectively, we can conclude that the experience was not destroyed, only the memory of it. The listener judges that the whole experience was bad because it ended badly. However, in reality, only the ending was bad. His assessment ignores the previous musical bliss and remembers only the bad moment.

Our remembering self is convincing us that certain situations, experiences, people even, are bad only because we had one bad moment with them. However, this is often not true and by convincing our minds that something is bad before we’re 100% certain that it’s bad, we might miss out on possible future pleasurable experiences.

“Odd as it may seem, I am my remembering self, and the experiencing self, who does my living, is like a stranger to me.” Daniel Kahneman

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