Noise, A Flaw in Human Judgment, Kahneman, Sibony and Sunstein, 2021

“Although it is often ignored, noise is a large source of malfunction in society. In a 1981 study, for example, 208 federal judges were asked to determine the appropriate sentences for the same 16 cases… The average difference between the sentences that two randomly chosen judges gave for the same crime was more than 3.5 years. Considering that the mean sentence was seven years, that was a disconcerting amount of noise.”

The Gist

The authors describe how we are all affected by the judgments of others, both professional and personal. Two factors impact on these judgments – bias and noise. Eliminating bias from judgments does not eliminate noise. Noise is randomness where we expect certainty and consistency. It affects judgments made by people from all walks of life: teams of surgeons, underwriters, child custody managers, asylum courts, interview panels, airport security.

What’s Good

Great examples of everyday errors and how even the most respected professionals are often oblivious to them.


‘Noise’ is rarely discussed, which given its importance is a curiosity in itself. Bias has an ‘explanatory charisma’ which means it is the default explanation for poor judgments.

Something to Try

One of the best ways to overcome noise it to use a decision observer to help apply decision hygiene: accuracy, not individual expression, is the goal.