Thinking, Fast and Slow

Thinking, Fast and Slow

Author: Daniel Kahneman


This book explores the errors that occur when we use cognitive shortcuts to make judgments. The author explores the spectrum of these heuristics and biases, and the research that has defined the subject over the decades. The author applies his extensive personal experience of the field, and he dedicated the book to Amos Tversky, his life-time friend and colleague; together they overturned the previous assumptions that ‘people are generally rational, and their thinking is normally sound’ (page 8).

Netherlands-4052 - Deep in Thought..... Dennis Jarvis on Flikr.
Netherlands-4052 – Deep in Thought….. Dennis Jarvis on Flikr.

The title of the book reflects the two modes of human thinking; the automatic, fast and unconscious System 1, and the effortful, slow and conscious System 2. System 1 is responsible for most of our thinking and it ‘operates automatically and cannot be turned off at will’ (page 25). This thinking mode is characterised by neglect of uncertainty and suppression of doubt, making it gullible and prone to the different types of cognitive errors the book explores. System 2 thinking on the other hand is deliberate and takes into consideration uncertainty and doubt. It is however usually only triggered ‘when things get difficult’, and it may be completely unaware of the errors that arise from System 1 thinking (page 28).

I'm thinking of... Davide Restivo on Flikr.
I’m thinking of… Davide Restivo on Flikr.

The book is forensic in discussing the heuristics and biases that influence individuals and groups. For example, it details the detrimental effect of anchoring on the judgment of professionals such estate agents and judges (page 119-121). The author reviewed how the availability heuristic sways our judgment by overemphasising the salient, the dramatic, and the vivid (page 130). We learn how representativeness and base rate neglect result in ‘an excessive willingness to predict the occurrence of unlikely events’ (page 150). We also see how hindsight bias makes us ‘prone to blame decision makers for good decisions that worked out badly and to give them too little credit for successful moves…’ (page 203). The book referred to the optimism bias and its close relationship to risk-taking, saying it ‘…may well be the most significant of the cognitive biases’ (page 255). The book argues that these and several other heuristics of judgment lead to error because they wrongly substitute one question by an easier one (page 130).

Golden Guy Balancing Risk. Scott Maxwell on Flikr.
Golden Guy Balancing Risk. Scott Maxwell on Flikr.

The author chose some some key ideas for particular emphasis. One of these is loss aversion, ‘the most significant contribution of psychology to behavioural economics’ (page 283). The author describes this concept as ‘a powerful conservative force that favors minimal changes from the status quo…’ (page 305). He also discussed its malign influence on all spheres of life such as law, business, and politics. The concept of loss aversion gave rise to Prospect theory (page 278), the groundbreaking idea that drastically altered economic thinking and earned the author the Nobel Prize in Economic Sciences in 2002.

By Zero grey - Own work, Public Domain,
By Zero greyOwn work, Public Domain,

Another key concept the book explores, relevant to all professionals, is the reliability of expert judgments. The author strongly argues that skilled people are vulnerable to heuristic errors, and he says some expert predictions are often not better than guesses. He goes further to say that ‘those with the most knowledge are often less reliable’ because they develop an enhanced illusion of skill and become unrealistically overconfident (page 219). He illustrated this with the specific example of healthcare, saying overconfidence is endemic in medicine. He supported this with research that shows 40% of confident physician diagnoses are proved wrong by post-mortem examinations (page 263).


The book is a repository of countless psychological concepts that influence our daily lives. For example, the author discusses priming, a concept that challenges ‘our self-image as conscious and autonomous authors of our judgments and our choices’ (page 55). He discussed cognitive strain, and how this may influence our judgment and creativity (page 60). Other ideas include ego depletion (page 42), embodied cognition (page 51), the conjunction fallacy (page 158), stereotyping (page 168), altruistic punishment (page 308), and regression to the mean (page 175). We learn of interestingly named concepts such as the Florida effect (page 53), the Lady Macbeth effect (page 56), the mere exposure effect (page 66), the halo effect (page 82), the hubris hypothesis (page 258), and competition neglect (page 259).  The book also discusses the illusions of causality (page 76), of patterns (page 117), of understanding (page 199), and of certainty (page 207).


Can we avoid the pitfalls of our cognitive biases? Can we do anything to prevent heuristic errors? The author is ‘generally not optimistic about the potential for personal control of biases’. He suggests that the best we can do is learn to recognise cognitive minefields and ‘seek reinforcement from System 2’ (page 28 and 417). He however makes many specific recommendations such as to ‘question the diagnosticity of your evidence’ (page 154), and to use reference class forecasting to mitigate the consequences of the planning fallacy (page 251).

By Kyösti Viinamäki, CC BY-SA 4.0,
By Kyösti Viinamäki, CC BY-SA 4.0,

Rather than express a dogmatic view of the field, the author paints ‘a richer and more balanced picture in which skill and heuristics are alternative sources of intuitive judgments and choices’ (page 11). For this reason the book made references to many other influential thinkers in the field of cognitive psychology. We learn of Cass Sunstein and Timur Kuran and their ideas on the availability cascade, ‘a self-sustaining chain of events which may start from media reports of a relatively minor event and lead up to public panic…’ (page 142). He referred to Paul Slovic and his work on the affect heuristic and why ‘people make judgments and decisions by consulting their emotions’ (page 139). He mentioned Richard Thaler in the context of his book, Nudge, and the endowment effect (page 292-293). He cited Nassim Taleb‘s The Black Swan as an important influence on his views about overconfidence (page 14). He also referred to other books such as  Creativity by Mihaly Csikszentmihalyi and The Wisdom of Crowds by James Surowiecki.


This is a detailed work, written by someone who practically defined the genre. The scope of topics he covers is breathtaking and unmatched by other books that have explored this subject. The book is a review of a lifetime of research which defined ‘heuristics and biases‘ and how they predispose to systematic errors. The author discusses complex concepts in very accessible language, and linked the research findings to their practical applications. Some of his views, particularly on expert judgments, differ from the experience of psychologists who study naturalistic decision making. These researchers, such as Gary Klein and Gerd Gigerenzer emphasise the value of intuitive judgments in their books Sources of Power and Gut Feelings. This book however discussed these differing opinions and tried to project a balanced view of the subject.

Overall assessment

The book covers the breadth of the factors that govern our thinking and behaviour. It is written by an expert who has been in the forefront of shaping the field. Many concepts discussed in the book have direct relevance to health care, and there are illustrative medical examples. The topic is particularly important for doctors and I highly recommend the book.

Book details

Publisher, Place, Year: Penguin Books, London, 2011
Number of Chapters: 38
Number of Pages: 499
Price: £7.69
Star Rating: 5 stars

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