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Summary: The Undoing Project: A Friendship That Changed Our Minds by Michael Lewis

The Undoing Project (2016) transports you into the intriguing minds of two revolutionary psychologists: Daniel Kahneman and Amos Tversky. This gripping narrative reveals their journey to reshape our understanding of human decision-making and how unseen biases are influencing us at every turn.

Introduction: Dive into the mysteries of human decision-making.

Have you ever wondered why some decisions seem so straightforward, while others feel like an uphill battle? Or pondered why, against all odds, you sometimes choose to take a gamble? Well, this is because human decision-making is a complex process. It’s deeply entwined with our emotions, biases, and the whole world around us.

In this condensed summary of The Undoing Project by Michael Lewis, you’ll discover two groundbreaking insights from two revolutionary psychologists, Daniel Kahneman and Amos Tversky. Together, they challenged conventional wisdom, redefined economic theory, and unveiled the fascinating complexity of human decision-making.

Summary: The Undoing Project: A Friendship That Changed Our Minds by Michael Lewis

Unmasking the human psyche

Growing up as a Jewish child during the German occupation of Paris, Danny Kahneman quickly realized that people were complex and endlessly fascinating.

Through his experiences – including eluding the Nazis, moving to Jerusalem during its independence war, and adapting to Israel’s diverse culture – he began to look at humans with a sense of detachment. So when Danny was tasked by the Israeli military to design a personality test to sort recruits, he began to get skeptical of the many subjective biases influencing human judgment.

His skepticism was particularly directed toward conventional stereotypes that associated specific personality traits with particular military roles – such as dominance for commanding officers, resilience for infantrymen, or analytical skills for intelligence officers. In addition, he noticed the halo effect, where an initial impression often shaped subsequent judgments about a person.

Determined to overcome this, Danny developed behavior-focused questions to assess the recruits’ suitability for different military roles. As his work grew, his results began to contradict these stereotypes, showing that successful individuals across different branches shared the same traits. These experiences laid the foundation for his later research on decision-making and cognitive biases, fundamentally reshaping our understanding of human behavior under uncertainty.

Years later, as a faculty member at the Hebrew University in Jerusalem, he formed a unique collaboration with a fellow psychologist, Amos Tversky. Danny had invited Amos, a psychologist known for his sharp insights, to give a guest lecture at one of his seminars around 1968. This invitation marked the beginning of their dynamic partnership.

Their first jointly written paper was published in 1971, sparking an intellectual union that would lead to several other influential publications. At the time, the conventional wisdom was rooted in a belief that human decisions were largely rational, and that specific personality traits predisposed people to certain roles or tasks. Their shared curiosity about human judgment under uncertainty led them to explore and challenge these established beliefs.

Together, they uncovered that people often rely on mental shortcuts, or heuristics, to make decisions. For instance, people draw on “representativeness,” comparing something to a mental model in their mind to make judgments. However, this reliance can often lead to serious miscalculations and systematic errors – like seeing patterns where none exist, or succumbing to stereotypes.

The saga of Kahneman and Tversky highlights a significant shift in our understanding of human behavior. The notion that humans always behave rationally, a cornerstone of traditional economic models, has been thoroughly challenged. Their work shows how our minds grapple with probabilities and uncertainties – a testament to the profound complexity of the human psyche.

Prospect theory, unraveled

Picture this: two researchers are flipping a coin, metaphorically speaking. But instead of flipping for the usual heads or tails, they’re flipping to observe something far more intriguing – human decisions under the risk of loss or the possibility of gain.

This brings us to the fascinating world of prospect theory that Amos and Danny championed. Classical economic theory postulates that humans are rational actors, making decisions with the final outcome in mind. But through prospect theory, Amos and Danny offered a twist. They asserted that people, rather than being solely rational, are also swayed by the potential value of losses and gains in their decision-making process.

Imagine you’re gambling. You’re not just thinking about the ultimate win or loss, right? You’re also considering how much you could lose in each bet, and how much you could potentially gain. This is the heart of prospect theory. It turns out we’re generally more willing to take risks to avoid losses than to achieve gains, signifying our inherent aversion to loss.

One compelling example of this is the Asian Disease Problem. In this hypothetical scenario, people are asked to choose between two public health strategies to combat a deadly disease – one framed in terms of lives saved and the other in terms of lives lost. Surprisingly, people tend to make different choices depending on the framing, even though the outcomes are numerically identical. It’s a situation that, when framed as a loss, leads people to be more willing to take risks. But when framed as a gain, people become risk-averse. It seems our reactions to risk can change based on how a situation is presented to us. And this discovery revolutionized our understanding of decision-making behavior.

So what can we learn from this? First, remember that people don’t always respond to probabilities rationally – emotion plays a significant role in decision-making. And as the odds become more remote, our emotional responses intensify. For example, we may feel an irrational fear of a one-in-a-billion chance of loss, or a similarly irrational hope for a one-in-a-billion chance of gain. Being aware of this bias can help us make more balanced decisions.

Second, when we’re making decisions, it’s important to be aware of how they’re framed. Is a situation being presented as a potential loss or a potential gain? Recognizing this can allow us to be more objective and less influenced by the framing effect.


Daniel Kahneman and Amos Tversky revolutionized our understanding of human behavior, showing how it’s influenced by biases, emotions, and the framing of choices. Their insights, captured in the prospect theory, reveal that we aren’t simply rational actors – we’re complex beings swayed by potential losses and gains. Their work emphasizes the importance of critical awareness in our decisions and provides a lens through which we can better engage with the world around us.

About the Author

Michael Lewis


Psychology, Biography, Memoir


“The Undoing Project: A Friendship That Changed Our Minds” is a captivating non-fiction book written by Michael Lewis. It explores the remarkable friendship and collaboration between two Israeli psychologists, Daniel Kahneman and Amos Tversky, and their groundbreaking contributions to the field of behavioral economics.

The book delves into the lives and work of Kahneman and Tversky, highlighting their significant impact on our understanding of human decision-making and the flaws in traditional economic theories that assume people always act rationally.

Lewis narrates the story of how the two psychologists met and developed a unique partnership, challenging prevailing beliefs about human behavior and decision-making. Their pioneering research explored cognitive biases, heuristics, and the irrational aspects of human thinking.
Throughout the book, Lewis provides examples of their experiments and studies, which shed light on the systematic errors and biases that affect our judgment and decision-making processes. The insights gained from their work have had far-reaching implications, influencing fields beyond economics, such as psychology, medicine, and public policy.

“The Undoing Project” also explores the personal dynamics between Kahneman and Tversky, their contrasting personalities, and the challenges they faced during their collaboration. Lewis skillfully portrays their friendship, including the intellectual debates, the highs and lows, and the ultimate dissolution of their partnership.

Additionally, the book touches upon the influence of their work on other prominent figures, such as Richard Thaler and the emergence of the field of behavioral economics. It showcases how their ideas challenged the prevailing economic theories, leading to a paradigm shift in understanding human behavior and decision-making.

Overall, “The Undoing Project” is a captivating and thought-provoking book that delves into the lives and work of Daniel Kahneman and Amos Tversky. Michael Lewis skillfully narrates their journey, highlighting their groundbreaking contributions to our understanding of human decision-making and the impact of their work on various disciplines.

“The Undoing Project” by Michael Lewis is a fascinating exploration of the friendship and intellectual collaboration between Daniel Kahneman and Amos Tversky, two Israeli psychologists who revolutionized the field of behavioral economics.

One of the strengths of this book is Lewis’s ability to bring the story to life, capturing the essence of Kahneman and Tversky’s unique partnership. The narrative is engaging and well-paced, providing readers with a deep understanding of their groundbreaking research and its implications. Lewis expertly weaves together personal anecdotes, scientific experiments, and historical context to create a compelling narrative.

The book excels in explaining complex concepts in an accessible manner, making it suitable for both experts and readers new to the subject. Lewis effectively breaks down the experiments and studies conducted by Kahneman and Tversky, illustrating the cognitive biases and heuristics that influence human decision-making. This allows readers to grasp the significance of their findings and understand how they challenged traditional economic theories.

Moreover, the book goes beyond the academic aspects and delves into the personal dynamics between Kahneman and Tversky. Lewis portrays their contrasting personalities, their intellectual debates, and the challenges they faced during their collaboration. This adds depth to the story, making it more relatable and human.

However, some readers might find the book’s narrative style and focus on personal stories to be more prominent than the scientific content. While it contributes to the overall storytelling, it could potentially leave readers wanting a deeper exploration of the psychological theories and methods employed by Kahneman and Tversky.

In conclusion, “The Undoing Project” is a well-crafted book that explores the remarkable friendship and intellectual partnership between Daniel Kahneman and Amos Tversky. Michael Lewis successfully brings their story to life, shedding light on their groundbreaking research and its impact on behavioral economics. This book is highly recommended for those interested in understanding the complexities of human decision-making and the individuals who reshaped our understanding of it.

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