Thinking, Fast and Slow quiz
Daniel Kahneman · 2011
Ten questions on Daniel Kahneman's key ideas, each with a short explanation. Read it a while ago? Take the quiz before you look at the summary: what you can recall now is what you'll keep.
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Question 1 of 10
A bat and a ball cost $1.10 together, and the bat costs $1 more than the ball. Most people's first answer for the ball is 10 cents. What does Kahneman take from this?
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B. An answer comes to mind and System 2 doesn't check it The ball costs 5 cents. Ten cents springs to mind at once, and checking it would take seconds, yet many students at elite universities didn't bother. For Kahneman this shows System 2 is lazy: it often endorses System 1's answer unchecked. And System 1 can't be switched off; you can only learn when to slow down.
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Question 2 of 10
You hear only the prosecution's side of a case and feel sure the defendant is guilty. What does the book say about that confidence?
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D. It reflects how coherent the story is, not how complete Kahneman calls this WYSIATI: what you see is all there is. System 1 builds the best story it can from what it's given and doesn't account for what's missing. In one study, people who heard only one side of a legal dispute were more confident in their verdicts than people who heard both sides.
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Question 3 of 10
Most people rank "Linda is a bank teller and active in the feminist movement" as more likely than "Linda is a bank teller." What's the error?
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A. Two things together can't be likelier than one alone Every feminist bank teller is a bank teller, so the longer description can't be more probable. Linda fits the stereotype of a feminist so well that System 1 judges by resemblance instead of probability. Kahneman and Tversky called this the conjunction fallacy, and it shows representativeness overriding logic.
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Question 4 of 10
In a negotiation, the other side opens with an outrageously high price. What does Kahneman suggest?
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C. Object openly and refuse to bargain from that figure An extreme counteroffer just leaves a gap that's hard to close later. Kahneman told his negotiation students to protest, even walk out, rather than bargain from that figure. Experience doesn't protect you: veteran German judges gave longer sentences after rolling a higher number on loaded dice.
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Question 5 of 10
An Israeli Air Force instructor told Kahneman that praise made cadets fly worse and yelling made them fly better. What was really going on?
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A. Unusual flights tend to be followed by more average ones Instructors praised flights that were unusually good and yelled after ones that were unusually bad. Luck plays a part in every attempt, so the next one tends to land closer to average either way. The instructor saw cause and effect where there was only regression to the mean.
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Question 6 of 10
The U.S. counties with the lowest kidney cancer rates are mostly rural and thinly populated. So are the counties with the highest rates. Why?
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C. Small populations produce extreme rates by chance A few cases more or fewer swing a small county's rate a lot, so small counties fill both ends of the ranking. Kahneman uses the example to show how fast System 1 reaches for causes, like clean country living or rural poverty, to explain what is really sampling noise.
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Question 7 of 10
You're planning a kitchen renovation and want a realistic timeline. Which approach does the book recommend?
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D. Start from how long similar renovations took, then adjust Detailed plans take the inside view and quietly assume things go smoothly: the planning fallacy. The outside view starts from a reference class. Kahneman learned this firsthand: his team expected to finish a textbook in about two years, similar teams that finished at all had needed seven to ten, and the book took eight.
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Question 8 of 10
You're offered a coin flip: heads, you win $150; tails, you lose $100. Most people turn it down. According to prospect theory, why?
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B. Losing $100 weighs more than winning $150 The bet favors you on average, but a loss weighs more than an equal gain, so the possible $100 loss outweighs the possible $150 win. Kahneman notes that many people want a chance to win about $200 before they'll risk $100. And people aren't always risk-averse: facing a sure loss, they often gamble.
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Question 9 of 10
Doctors were told the short-term outcome of lung cancer surgery in one of two ways. What did the study find?
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C. More chose surgery when told 90% survive the first month The two statements mean the same thing, yet 84% of physicians favored surgery in the survival version and 50% in the mortality version. System 1 responds to the emotional pull of survival versus death, not to the arithmetic, and medical training doesn't protect against framing.
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Question 10 of 10
In the cold-hand experiment, one trial was 60 seconds in painfully cold water; the other added 30 seconds of slightly less cold water. Which did most people choose to repeat?
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A. The longer one, because its ending felt milder Most picked the longer trial, though it meant more pain overall. Memory neglects duration and rates an experience by its peak and its end. The remembering self makes the choice, so people chose the trial they remembered as less bad, not the one that actually hurt less.
Thinking, Fast and Slow in one paragraph
Thinking, Fast and Slow explains why smart people make predictable mistakes. Daniel Kahneman describes two modes of thought: a fast, intuitive System 1 and a slow, deliberate System 2 that is too lazy to check most of what the first one suggests. Drawing on decades of experiments, many run with Amos Tversky, he shows how this leads to biased judgments, overconfidence, and choices that bend to wording and the fear of loss. His aim is a shared vocabulary for spotting these errors, which is easier in others than in ourselves.
The 9 key ideas of Thinking, Fast and Slow
Two systems run your mind
System 1 is fast and automatic: it knows 2 + 2, reads anger in a face and drives a car down an empty road. System 2 is slow and effortful: it works out 17 × 24 and checks whether an argument holds. Kahneman calls them characters in a story, not parts of the brain. System 2 thinks it's in charge, but it's lazy and often signs off on whatever System 1 proposes.
Coherent stories hide missing evidence
System 1 builds the most coherent story it can from the information at hand and never asks what's missing. Kahneman's shorthand is WYSIATI. Confidence tracks how well the story hangs together, not how much evidence stands behind it, so a little information can feel more convincing than a lot. The halo effect is one result: one good trait colors everything else you think about a person.
Hard questions get easy answers
Faced with a hard question, System 1 quietly answers an easier one, and you rarely notice the swap. Asked how likely something is, you judge how easily examples come to mind (availability) or how well it fits a stereotype (representativeness). That's why most people say Linda, a philosophy graduate who protested as a student, is more likely a feminist bank teller than a bank teller, though that can't be more probable.
Any number can become an anchor
Estimates drift toward whatever number you saw first, even one you know is random. Kahneman describes two routes: System 2 adjusts away from the anchor but stops too soon, and System 1 is primed by it, so evidence that fits the number comes to mind first. Experienced German judges who rolled loaded dice gave longer sentences after a higher roll. Asking prices and opening offers work the same way.
We see causes in chance
System 1 hunts for causes, so it reads stories into randomness. Small samples swing to extremes more often than large ones, which is why the U.S. counties with the lowest kidney cancer rates and those with the highest look alike: mostly rural and thinly populated. Extreme results also tend to be followed by more ordinary ones, and this regression to the mean gets mistaken for the effect of whatever happened in between.
Confidence doesn't mean accuracy
We trust our judgments far more than their record deserves. Most stock pickers' results look more like luck than skill, and simple formulas often beat expert judgment. Plans fall into the planning fallacy: built from the inside view, they assume things go as planned. The fix is the outside view: start from how similar projects actually turned out. Expert intuition earns trust only in regular settings where long practice brings quick, clear feedback.
Losses hurt more than gains please
Prospect theory, which Kahneman developed with Tversky and which was central to his Nobel Prize, says we judge outcomes as gains and losses from a reference point, not as total wealth. A loss hurts roughly twice as much as an equal gain feels good. That's why people turn down favorable bets, and why owners demand more to give up a mug than buyers will pay for it: the endowment effect.
The frame changes the choice
Two descriptions of the same facts can lead to different choices, because System 1 reacts to the words, not the math. Doctors were more willing to recommend surgery when told of a 90% one-month survival rate than when told of 10% mortality. Defaults are frames too: organ donation is far more common where people must opt out than where they must opt in. Kahneman's remedy is broad framing: treat each risky choice as one of many.
Your two selves keep different scores
The experiencing self lives through each moment; the remembering self keeps the story, and it's the one that makes decisions. Memory largely ignores how long an experience lasted (duration neglect) and rates it by its most intense moment and its end (the peak-end rule). So adding a milder stretch to the end of a painful procedure can make it remembered as less bad, even though it adds pain in total.
Has it held up?
Parts of the book have not survived the replication crisis that shook psychology in the years after it came out. The chapter on priming, which told readers that "disbelief is not an option," leaned on small studies such as one in which unscrambling words linked to old age made people walk more slowly. A 2012 replication that timed walkers automatically found no effect, except when the experimenters expected one. Ego depletion, the idea that self-control draws on a limited store of energy, fared no better: a 2016 replication across 23 labs found an effect close to zero.
Kahneman said so himself. In 2012 he wrote to priming researchers warning of a "train wreck looming." In 2017, replying to an analysis of the studies behind his priming chapter, he wrote that he had placed too much faith in underpowered studies and that behavioral priming effects can't be as large and robust as the chapter suggested, though he still believed they exist.
The core of the book holds up much better. The Many Labs project, which reran 13 well-known findings in 36 samples, reproduced anchoring strongly, along with the gain-versus-loss framing effect. A 2020 study in 19 countries replicated the patterns behind prospect theory for nearly all of the original items. How large loss aversion is, and when it appears, is still debated.
Sources
- Doyen, S., Klein, O., Pichon, C.-L., & Cleeremans, A. (2012). Behavioral priming: It's all in the mind, but whose mind? PLoS ONE, 7(1), e29081.
- Hagger, M. S., Chatzisarantis, N. L. D., Alberts, H., Anggono, C. O., Batailler, C., et al. (2016). A multilab preregistered replication of the ego-depletion effect. Perspectives on Psychological Science, 11(4), 546–573.
- Yong, E. (2012, October 3). Nobel laureate challenges psychologists to clean up their act. Nature.
- Schimmack, U., Heene, M., & Kesavan, K. (2017, February 2). Reconstruction of a train wreck: How priming research went off the rails [Blog post, with a comment by D. Kahneman, February 14, 2017]. Replicability-Index.
- Klein, R. A., Ratliff, K. A., Vianello, M., et al. (2014). Investigating variation in replicability: A "many labs" replication project. Social Psychology, 45(3), 142–152.
- Ruggeri, K., Alí, S., Berge, M. L., et al. (2020). Replicating patterns of prospect theory for decision under risk. Nature Human Behaviour, 4(6), 622–633.
- Gal, D., & Rucker, D. D. (2018). The loss of loss aversion: Will it loom larger than its gain? Journal of Consumer Psychology, 28(3), 497–516.
Thinking, Fast and Slow book club questions
10 questions for a book club or a class, from first reactions to where the book can be argued with. They work best once everyone has finished it. For questions that work with any nonfiction book and a plan for the evening, see our book club questions guide.
- Which experiment in the book caught you out most, such as the bat and the ball, Linda the bank teller or the cold-hand study, and how did it feel to fall for it?
- Kahneman hoped to give readers words for spotting errors in judgment. Which term from the book, such as WYSIATI, anchoring or the planning fallacy, do you expect to keep using, and why?
- Kahneman says confidence comes from how coherent a story feels, not how much evidence stands behind it. Where do you see this in the news, at work or in your snap judgments about people?
- If losses hurt about twice as much as equal gains please, how might that shape decisions like changing jobs, selling a house or abandoning a project that is clearly failing?
- Defaults steer choices without forcing them: organ donation is far more common where people must opt out. When is it fair for governments or companies to set defaults, and when is that manipulation?
- The remembering self, not the experiencing self, makes most of our choices. Should we plan vacations, careers and medical care around how they feel in the moment or how we will remember them?
- Kahneman later admitted his priming chapter relied on small studies that failed to replicate. How should that affect how you read the rest of the book, and what did he earn by saying so?
- Critics such as Gerd Gigerenzer argue that mental shortcuts often serve people well outside the lab. Is the book too hard on System 1, and when have your quick intuitions proved right?
- Think of a project that ran late or over budget. What would the outside view, starting from how similar projects actually turned out, have told you at the start?
- Kahneman thinks errors are easier to spot in others than in ourselves, so groups may catch what individuals miss. What one check could your team or family add before a big decision?
How to remember Thinking, Fast and Slow
Taking the quiz above was already the most useful thing you can do with a book you've read. Pulling an idea out of memory strengthens it far more than reading a summary again; psychologists call it active recall. The questions you got wrong are the ideas that were slipping away.
What keeps them is timing. Memory fades on a curve, quickly at first, so the next review works best in about three days, then a week later, then a few weeks after that. Our review schedule calculator gives you the exact dates, and how to remember what you read covers the whole method.
