How are human judgments and decisions made?

Photo: Sushil Nash

Noise. A flaw in human judgment
Daniel Kahneman, Cass R. Sunstein and Olivier Sibony
Translation by Joaquín Chamorro Mielke. Debate. Barcelona, ​​2021. 494 pages. € 22.90. Ebook: € 10.99

Daniel Kahneman, Professor of Psychology at Princeton University, received the 2002 Nobel Prize in Economics. The son of Lithuanian Jews who emigrated to Paris in the early 1920s, he was born in Tel Aviv in 1934 on the occasion of a visit by his mother to relatives settled in Palestine. After the Second World War, his family left France to settle in Israel.

After graduating in psychology from the Hebrew University of Jerusalem and completing his military service in the psychological analysis unit of the Israeli Armed Forces, he was awarded a scholarship to further studies at different American universities. Installed in the United States, his university work stands out for a brilliant ability to integrate psychology and economics. His contribution to behavioral economics, and his research on the psychology of judgment and decision-making in times of risk and uncertainty, will open the doors to the Nobel Prize for him.

The subtitle of Noise, A flaw in human judgment, is a clear indication of its content: a lucid attempt to avoid errors in the judgments we form and in the decisions we make. At the same time, it reveals that it is, to a large extent, the continuation of Think fast, think slow. An innovative explanation of the way we think and make our judgments based on the articulation of a System 1, fast, intuitive and emotional, with a System 2, slower, deliberative and logical. Published in 2011, this first outreach book by Kahneman provides powerful insight into how decisions are made in personal or professional life. Despite its almost 700 dense pages, it immediately became a worldwide success.


Human error is, as we have just noted, the issue of Noise, a text that has the collaboration of Olivier Sibony, “writer and consultant specialized in strategic decision making”, and Cass R. Sunstein, “the most cited law professor in the United States”, columnist and author of Rumorology. Two powerful vectors center the result of this team effort. On the one hand, the meticulous description of the numerous biases that lead to error in judgment and, on the other, coining the concept of noise as the effect of variability in judgment. If a lot has been written about bias, little is known about the notion of noise understood “as an unwanted variability in judgments about the same problem” due to its subtlety. Noise is difficult to detect in single decisions but organizations must take steps to control it in the individual judgments of their members.

This book illustrates vitally relevant cognitive mechanisms, biases and errors that determine our life, both daily and institutional.

Often biases – specific errors – and noises are mixed and it is necessary to distinguish the role of one and the other. If bias is the protagonist of the show, noise is a supporting actor. However, noise is sometimes decisive and is present in fields such as medicine, the judiciary, personnel selection, or forensic science, for example.

The authors’ journey, illustrated with specific cases, through knowledge in which errors occur is wide and surprising. Let us stop at one of special significance. On March 11, 2004 (11-M), ten explosives placed by terrorists exploded on four trains on the Madrid commuter network. 193 people died and around 2,000 were injured. The police find a fingerprint in a plastic bag at the crime scene and via Interpol it reaches the FBI crime lab. In a few days the footprint is identified: it belongs to Brandon Mayfield, a former US Army officer, living in Oregon, married to an Egyptian and converted to Islam. As a lawyer, he had defended people convicted of moving to Afghanistan to join the Taliban. FBI surveillance did not reveal any important information, despite which he was arrested.

During the arrest, the Spanish police informed the FBI of the mismatch between the fingerprint on the plastic bag and Mayfield’s. In two weeks, the detainee was released and received compensation of two million dollars from the United States Government. Do youHow America’s Best Fingerprint Writers Could Make a Mistake in Identifying a Citizen’s Fingerprint who hadn’t left Oregon for ten years? The answer will be found by the reader in the pages of a book that illustrates cognitive mechanisms of vital relevance in both daily and institutional life.

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How are human judgments and decisions made?