Thinking, Fast and Slow

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Thinking, Fast and Slow
Hardcover edition
AuthorDaniel Kahneman
CountryUnited States
LanguageEnglish language
PublisherFarrar, Straus and Giroux
Publication date
Media typePrint (hardcover, paperback), audio
Pages499 pages

Thinking, Fast and Slow is a 2011 popular science book by psychologist Daniel Kahneman. The book's main thesis is a differentiation between two modes of thought: "System 1" is fast, instinctive and emotional; "System 2" is slower, more deliberative, and more logical.

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.[1] Kahneman performed his own research, often in collaboration with Amos Tversky, which enriched his experience to write the book.[2][3] It covers different phases of his career: his early work concerning cognitive biases, his work on prospect theory and happiness, and with the Israel Defense Forces.

The book was a New York Times bestseller[4] and was the 2012 winner of the National Academies Communication Award for best creative work that helps the public understanding of topics in behavioral science, engineering and medicine.[5] The integrity of some priming studies cited in the book has been called into question in the midst of the psychological replication crisis.[6]

Two systems[edit]

In the book's first section, Kahneman describes two different ways the brain forms thoughts:

  • System 1: Fast, automatic, frequent, emotional, stereotypic, unconscious. Examples (in order of complexity) of things system 1 can do:
    • determine that an object is at a greater distance than another
    • localize the source of a specific sound
    • complete the phrase "war and ..."
    • display disgust when seeing a gruesome image
    • solve 2+2=?
    • read text on a billboard
    • drive a car on an empty road
    • think of a good chess move (if you're a chess master)
    • understand simple sentences
    • associate the description 'quiet and structured person with an eye for details' with a specific job
  • System 2: Slow, effortful, infrequent, logical, calculating, conscious. Examples of things system 2 can do:
    • prepare yourself for the start of a sprint
    • direct your attention towards the clowns at the circus
    • direct your attention towards someone at a loud party
    • look for the woman with the grey hair
    • try to recognize a sound
    • sustain a faster-than-normal walking rate
    • determine the appropriateness of a particular behavior in a social setting
    • count the number of A's in a certain text
    • give someone your telephone number
    • park into a tight parking space
    • determine the price/quality ratio of two washing machines
    • determine the validity of a complex logical reasoning
    • solve 17 × 24

Kahneman describes a number of experiments which purport to examine the differences between these two thought systems and how they arrive at different results even given the same inputs. Terms and concepts include coherence, attention, laziness, association, jumping to conclusions, WYSIATI (What you see is all there is), and how one forms judgments. The System 1 vs. System 2 debate includes the reasoning or lack thereof for human decision making, with big implications for many areas including law and market research.[7]

Heuristics and biases[edit]

The second section offers explanations for why humans struggle to think statistically. It begins by documenting a variety of situations in which we either arrive at binary decisions or fail to associate precisely reasonable probabilities with outcomes. Kahneman explains this phenomenon using the theory of heuristics. Kahneman and Tversky originally discussed this topic in their 1974 article titled Judgment Under Uncertainty: Heuristics and Biases.[8]

Kahneman uses heuristics to assert that System 1 thinking involves associating new information with existing patterns, or thoughts, rather than creating new patterns for each new experience. For example, a child who has only seen shapes with straight edges might perceive an octagon when first viewing a circle. As a legal metaphor, a judge limited to heuristic thinking would only be able to think of similar historical cases when presented with a new dispute, rather than considering the unique aspects of that case. In addition to offering an explanation for the statistical problem, the theory also offers an explanation for human biases.


The "anchoring effect" names a tendency to be influenced by irrelevant numbers. Shown greater/lesser numbers, experimental subjects gave greater/lesser responses.[2] As an example, most people, when asked whether Gandhi was more than 114 years old when he died, will provide a much greater estimate of his age at death than others who were asked whether Gandhi was more or less than 35 years old. Experiments show that people's behavior is influenced, much more than they are aware, by irrelevant information.


The availability heuristic is a mental shortcut that occurs when people make judgments about the probability of events on the basis of how easy it is to think of examples. The availability heuristic operates on the notion that, "if you can think of it, it must be important". The availability of consequences associated with an action is related positively to perceptions of the magnitude of the consequences of that action. In other words, the easier it is to recall the consequences of something, the greater we perceive these consequences to be. Sometimes, this heuristic is beneficial, but the frequencies at which events come to mind are usually not accurate representations of the probabilities of such events in real life.[9][10]

Conjunction fallacy[edit]

System 1 is prone to substituting a simpler question for a difficult one. In what Kahneman terms their "best-known and most controversial" experiment, "the Linda problem," subjects were told about an imaginary Linda, young, single, outspoken, and intelligent, who, as a student, was very concerned with discrimination and social justice. They asked whether it was more probable that Linda is a bank teller or that she is a bank teller and an active feminist. The overwhelming response was that "feminist bank teller" was more likely than "bank teller," violating the laws of probability. (All feminist bank tellers are bank tellers, so the former can't be more likely). In this case System 1 substituted the easier question, "Is Linda a feminist?", neglecting the occupation qualifier. An alternative interpretation is that the subjects added an unstated cultural implicature to the effect that the other answer implied an exclusive or, that Linda was not a feminist.[2]

Optimism and loss aversion[edit]

Kahneman writes of a "pervasive optimistic bias", which "may well be the most significant of the cognitive biases." This bias generates the illusion of control: the illusion that we have substantial control of our lives.

A natural experiment reveals the prevalence of one kind of unwarranted optimism. The planning fallacy is the tendency to overestimate benefits and underestimate costs, impelling people to begin risky projects. In 2002, American kitchen remodeling was expected on average to cost $18,658, but actually cost $38,769.[2]

To explain overconfidence, Kahneman introduces the concept he terms What You See Is All There Is (WYSIATI). This theory states that when the mind makes decisions, it deals primarily with Known Knowns, phenomena it has observed already. It rarely considers Known Unknowns, phenomena that it knows to be relevant but about which it does not have information. Finally it appears oblivious to the possibility of Unknown Unknowns, unknown phenomena of unknown relevance.

He explains that humans fail to take into account complexity and that their understanding of the world consists of a small and necessarily un-representative set of observations. Furthermore, the mind generally does not account for the role of chance and therefore falsely assumes that a future event will be similar to a past event.


Framing is the context in which choices are presented. Experiment: subjects were asked whether they would opt for surgery if the "survival" rate is 90 percent, while others were told that the mortality rate is 10 percent. The first framing increased acceptance, even though the situation was no different.[11]

Sunk cost[edit]

Rather than consider the odds that an incremental investment would produce a positive return, people tend to "throw good money after bad" and continue investing in projects with poor prospects that have already consumed significant resources. In part this is to avoid feelings of regret.[11]


This part (part III, sections 19–24) of the book is dedicated to the undue confidence in what the mind believes it knows. It suggests that people often overestimate how much they understand about the world and underestimate the role of chance in particular. This is related to the excessive certainty of hindsight, when an event seems to be understood after it has occurred or developed. Kahneman's opinions concerning overconfidence are influenced by Nassim Nicholas Taleb.[12]


In this section Kahneman returns to economics and expands his seminal work on Prospect Theory. He discusses the tendency for problems to be addressed in isolation and how, when other reference points are considered, the choice of that reference point (called a frame) has a disproportionate effect on the outcome. This section also offers advice on how some of the shortcomings of System 1 thinking can be avoided.

Prospect theory[edit]

Kahneman developed prospect theory, the basis for his Nobel prize, to account for experimental errors he noticed in Daniel Bernoulli's traditional utility theory.[13] According to Kahneman, Utility Theory makes logical assumptions of economic rationality that do not represent people's actual choices, and does not take into account cognitive biases.

One example is that people are loss-averse: they are more likely to act to avert a loss than to achieve a gain. Another example is that the value people place on a change in probability (e.g., of winning something) depends on the reference point: people seem to place greater value on a change from 0% to 10% (going from impossibility to possibility) than from, say, 45% to 55%, and they place the greatest value of all on a change from 90% to 100% (going from possibility to certainty). This occurs despite the fact that by traditional utility theory all three changes give the same increase in utility. Consistent with loss-aversion, the order of the first and third of those is reversed when the event is presented as losing rather than winning something: there, the greatest value is placed on eliminating the probability of a loss to 0.

After the book's publication, the Journal of Economic Literature published a discussion of its parts concerning prospect theory,[14] as well as an analysis of the four fundamental factors on which it is based.[15]

Two selves[edit]

The fifth part of the book describes recent evidence which introduces a distinction between two selves, the 'experiencing self' and 'remembering self'.[16] Kahneman proposed an alternative measure that assessed pleasure or pain sampled from moment to moment, and then summed over time. Kahneman termed this "experienced" well-being and attached it to a separate "self." He distinguished this from the "remembered" well-being that the polls had attempted to measure. He found that these two measures of happiness diverged.[17]

Life as a story[edit]

The author's significant discovery was that the remembering self does not care about the duration of a pleasant or unpleasant experience. Instead, it retrospectively rates an experience by the maximum or minimum of the experience, and by the way it ends. The remembering self dominated the patient's ultimate conclusion.

"Odd as it may seem," Kahneman writes, "I am my remembering self, and the experiencing self, who does my living, is like a stranger to me."[3]

Experienced well-being[edit]

Kahneman first began the study of well-being in the 1990s. At the time most happiness research relied on polls about life satisfaction. Having previously studied unreliable memories, the author was doubtful that life satisfaction was a good indicator of happiness. He designed a question that emphasized instead the well-being of the experiencing self. The author proposed that "Helen was happy in the month of March" if she spent most of her time engaged in activities that she would rather continue than stop, little time in situations that she wished to escape, and not too much time in a neutral state that wouldn't prefer continuing or stopping the activity either way.

Thinking about life[edit]

Kahneman suggests that emphasizing a life event such as a marriage or a new car can provide a distorted illusion of its true value. This "focusing illusion" revisits earlier ideas of substituting difficult questions and WYSIATI.

Awards and honors[edit]


As of 2012 the book had sold over one million copies.[23] On the year of its publication, it was on the New York Times Bestseller List.[4] The book was reviewed in media including the Huffington Post,[24] The Guardian,[25] The New York Times,[2] The Financial Times,[26] The Independent,[27] Bloomberg[11] and The New York Review of Books.[28][further explanation needed]

The book was also widely reviewed in academic journals, including the Journal of Economic Literature,[14] American Journal of Education,[29] The American Journal of Psychology,[30] Planning Theory,[31] The American Economist,[32] The Journal of Risk and Insurance,[33] The Michigan Law Review,[34] American Scientist,[35] Contemporary Sociology,[36] Science,[37] Contexts,[38] The Wilson Quarterly,[39] Technical Communication,[40] The University of Toronto Law Journal,[41] A Review of General Semantics[42] and Scientific American Mind.[43] The book was also reviewed in a monthly magazine Observer, published by the Association for Psychological Science.[44][further explanation needed]

The book has achieved a large following among baseball scouts and baseball executives. The ways of thinking described in the book are believed to help scouts, who have to make major judgements off little information and can easily fall into prescriptive yet inaccurate patterns of analysis.[45]

The last chapter of Paul Bloom's Against Empathy discusses concepts also touched in Daniel Kahneman's book, Thinking, Fast and Slow, that suggest people make a series of rational and irrational decisions.[46][46]: 214  He criticizes the argument that "regardless of reason's virtues, we just aren't any good at it." His point is that people are not as "stupid as scholars think they are."[46]: 216  He explains that people are rational because they make thoughtful decisions in their everyday lives. For example, when someone has to make a big life decision they critically assess the outcomes, consequences, and alternative options.[46]: 230 

Author Nicholas Taleb has equated the book's importance to that of Adam Smith’s “The Wealth of Nations” and Sigmund Freud’s “The Interpretation of Dreams.”[47]

Replication crisis[edit]

Part of the book has been swept up in the replication crisis facing psychology and the social sciences. It was discovered many prominent research findings were difficult or impossible for others to replicate, and thus the original findings were called into question. An analysis[48] of the studies cited in chapter 4, "The Associative Machine", found that their replicability index (R-index)[49] is 14, indicating essentially low to no reliability. Kahneman himself responded to the study in blog comments and acknowledged the chapter's shortcomings: "I placed too much faith in underpowered studies."[50] Others have noted the irony in the fact that Kahneman made a mistake in judgment similar to the ones he studied.[51]

A later analysis[52] made a bolder claim that, despite Kahneman's previous contributions to the field of decision making, most of the book's ideas are based on 'scientific literature with shaky foundations'. A general lack of replication in the empirical studies cited in the book was given as a justification.

See also[edit]


  1. ^ Shaw, Tamsin (April 20, 2017). "Invisible Manipulators of Your Mind". New York Review of Books. ISSN 0028-7504. Retrieved August 10, 2020.
  2. ^ a b c d e Holt, Jim (November 27, 2011). "Two Brains Running". The New York Times. p. 16.
  3. ^ a b Daniel Kahneman (2011). Thinking, Fast and Slow. Macmillan. ISBN 978-1-4299-6935-2. Retrieved April 8, 2012.
  4. ^ a b "The New York Times Best Seller List – December 25, 2011" (PDF). Retrieved August 17, 2014.
  5. ^ a b "Daniel Kahneman's Thinking, Fast and Slow Wins Best Book Award From Academies; Milwaukee Journal Sentinel, Slate Magazine, and WGBH/NOVA Also Take Top Prizes in Awards' 10th Year". Retrieved March 10, 2018.
  6. ^ Schimmack, Ulrich (December 30, 2020). "A Meta-Scientific Perspective on "Thinking: Fast and Slow". Replicability-Index. Retrieved February 11, 2023.
  7. ^ "Web Page Under Construction".
  8. ^ Tversky, Amos; Kahneman, Daniel (1974). "Judgment under Uncertainty: Heuristics and Biases" (PDF). Science. 185 (4157): 1124–31. Bibcode:1974Sci...185.1124T. doi:10.1126/science.185.4157.1124. PMID 17835457. S2CID 143452957. Archived from the original on March 18, 2012.{{cite journal}}: CS1 maint: bot: original URL status unknown (link)
  9. ^ Tversky, Amos (1982). "11 – Availability: A heuristic for judging frequency and probability" (PDF). In Kahneman, Daniel (ed.). Judgment under uncertainty : heuristics and biases. Vol. 185. Cambridge [u.a.]: Cambridge Univ. Press. pp. 1124–31. Bibcode:1974Sci...185.1124T. doi:10.1126/science.185.4157.1124. ISBN 9780521240642. PMID 17835457. S2CID 143452957. {{cite book}}: |journal= ignored (help)
  10. ^ Tversky, Amos; Kahneman, Daniel (September 1973). "Availability: A heuristic for judging frequency and probability". Cognitive Psychology. 5 (2): 207–232. doi:10.1016/0010-0285(73)90033-9.(subscription required)
  11. ^ a b c Reprints, Roger Lowenstein (October 28, 2011). "Book Review: Thinking, Fast and Slow by Daniel Kahneman". Retrieved May 27, 2016.
  12. ^ Kahneman, Daniel (2011). Thinking, fast and slow. London: Penguin Books. pp. 14. ISBN 9780141033570. OCLC 781497062.
  13. ^ Kahneman, Daniel; Tversky, Amos (March 1979). "Prospect Theory: An Analysis of Decision under Risk" (PDF). Econometrica. 47 (2): 263–291. CiteSeerX doi:10.2307/1914185. JSTOR 1914185. Archived from the original on November 17, 2014.{{cite journal}}: CS1 maint: unfit URL (link)
  14. ^ a b Psychologists at the Gate: A Review of Daniel Kahneman's Thinking, Fast and Slow (PDF). 2012.
  15. ^ Psychologists at the Gate: A Review of Daniel Kahneman's Thinking, Fast and Slow (PDF). 2012. pp. 7–9.
  16. ^ Lazari-Radek, Katarzyna de; Singer, Peter (2014). The Point of View of the Universe: Sidgwick and Contemporary Ethics. Oxford University Press. p. 276.
  17. ^ Kahneman, Daniel (2011). "35. Two Selves". Thinking, Fast and Slow. New York: Farrar, Straus & Giroux.
  18. ^ "2011 Los Angeles Times Book Prize Winners & Finalists". Los Angeles Times. Archived from the original on April 16, 2016.
  19. ^ "10 Best Books of 2011". The New York Times. November 30, 2011. ISSN 0362-4331. Retrieved March 10, 2018.
  20. ^ Stein, Janice Gross; et al. "The Globe 100: The very best books of 2011". Retrieved March 10, 2018.
  21. ^ "The Economist - Books of the Year 2011 (50 books)".
  22. ^ "The Best Nonfiction of 2011". Wall Street Journal. December 17, 2011.
  23. ^ Cooper, Glenda (July 14, 2012). "Thinking, Fast and Slow: the 'landmark in social thought' going head to head with Fifty Shades of Grey". Daily Telegraph. ISSN 0307-1235. Retrieved February 17, 2018.
  24. ^ Levine, David K. (September 22, 2012). "Thinking Fast and Slow and Poorly and Well". Huffington Post. Retrieved February 17, 2018.
  25. ^ Strawson, Galen (December 13, 2011). "Thinking, Fast and Slow by Daniel Kahneman – review". the Guardian. Retrieved February 17, 2018.
  26. ^ "Thinking, Fast and Slow". Financial Times. November 5, 2011. Retrieved February 17, 2018.
  27. ^ "Thinking, Fast and Slow, By Daniel Kahneman". The Independent. November 18, 2011. Archived from the original on May 7, 2022. Retrieved February 17, 2018.
  28. ^ Dyson, Freeman (December 22, 2011). "How to Dispel Your Illusions". The New York Review of Books. ISSN 0028-7504. Retrieved February 17, 2018.
  29. ^ Durr, Tony (February 1, 2014). "Thinking, Fast and Slow by Daniel Kahneman". American Journal of Education. 120 (2): 287–291. doi:10.1086/674372. ISSN 0195-6744.
  30. ^ Krueger, Joachim I. (2012). Kahneman, Daniel (ed.). "Reviewing, Fast and Slow". The American Journal of Psychology. 125 (3): 382–385. doi:10.5406/amerjpsyc.125.3.0382. JSTOR 10.5406/amerjpsyc.125.3.0382.
  31. ^ Baum, Howell (2013). "Review of Thinking, fast and slow". Planning Theory. 12 (4): 442–446. doi:10.1177/1473095213486667. JSTOR 26166233. S2CID 149027956.
  32. ^ Brock, John R. (2012). "Review of Thinking, Fast and Slow". The American Economist. 57 (2): 259–261. doi:10.1177/056943451205700211. JSTOR 43664727. S2CID 149090700.
  33. ^ Gardner, Lisa A. (2012). "Review of Thinking, Fast and Slow". The Journal of Risk and Insurance. 79 (4): 1143–1145. doi:10.1111/j.1539-6975.2012.01494.x. JSTOR 23354961.
  34. ^ Stein, Alex (2013). "Are People Probabilistically Challenged?". Michigan Law Review. 111 (6): 855–875. JSTOR 23812713.
  35. ^ Sloman, Steven (2012). "The Battle Between Intuition and Deliberation". American Scientist. 100 (1): 73–75. JSTOR 23222820.
  36. ^ Etzioni, Amitai (2012). Kahneman, Daniel (ed.). "The End of Rationality?". Contemporary Sociology. 41 (5): 594–597. doi:10.1177/0094306112457657b. JSTOR 41722908. S2CID 143107781.
  37. ^ Sherman, Steven J. (2011). "Blink with Muscles". Science. 334 (6059): 1062–1064. Bibcode:2011Sci...334.1062S. doi:10.1126/science.1214243. JSTOR 41351778. S2CID 145337277.
  38. ^ jasper, james m. (2012). "thinking in context". Contexts. 11 (2): 70–71. doi:10.1177/1536504212446467. JSTOR 41960818.
  39. ^ Akst, Daniel (2011). "Rushing to Judgment". The Wilson Quarterly. 35 (4): 97–98. JSTOR 41484407.
  40. ^ Harrison, Kelly A. (2012). "Review of Thinking, Fast and Slow". Technical Communication. 59 (4): 342–343. JSTOR 43093040.
  41. ^ Richardson, Megan Lloyd (2012). "Review of Thinking, Fast and Slow [sic, included in a set of reviews]". The University of Toronto Law Journal. 62 (3): 453–457. doi:10.1353/tlj.2012.0013. JSTOR 23263811. S2CID 144044453.
  42. ^ Vassallo, Philip (2012). "Review of Thinking, Fast and Slow". ETC: A Review of General Semantics. 69 (4): 480. JSTOR 42579224.
  43. ^ Upson, Sandra (2012). "Cognitive Illusions". Scientific American Mind. 22 (6): 68–69. JSTOR 24943506.
  44. ^ Bazerman, Max H. (October 21, 2011). "Review of Thinking, Fast and Slow by Daniel Kahneman". APS Observer. 24 (10).
  45. ^ This Book Is Not About Baseball. But Baseball Teams Swear by It.
  46. ^ a b c d Bloom, Paul (2016). Against Empathy: The Case for Rational Compassion. Ecco. ISBN 978-0-06-233935-5.
  47. ^ Jr, Robert D. Hershey (March 27, 2024). "Daniel Kahneman, Who Plumbed the Psychology of Economics, Dies at 90". The New York Times. ISSN 0362-4331. Retrieved March 29, 2024.
  48. ^ R, Dr (February 2, 2017). "Reconstruction of a Train Wreck: How Priming Research Went off the Rails". Replicability-Index. Retrieved April 30, 2019.
  49. ^ R, Dr (January 31, 2016). "A Revised Introduction to the R-Index". Replicability-Index. Retrieved April 30, 2019.
  50. ^ McCook, Alison (February 20, 2017). ""I placed too much faith in underpowered studies:" Nobel Prize winner admits mistakes". Retraction Watch. Retrieved April 30, 2019.
  51. ^ Engber, Daniel (December 21, 2016). "How a Pioneer in the Science of Mistakes Ended Up Mistaken". Slate Magazine. Retrieved April 30, 2019.
  52. ^ Schimmack, Ulrich (December 30, 2020). "A Meta-Scientific Perspective on "Thinking: Fast and Slow". Replicability-Index. Retrieved February 21, 2021.

External links[edit]