These inconsistencies are all about noise, which Kahneman, Sibony and Sunstein define as “unwanted variability in judgments.”
Sometimes we treasure variability — in artistic tastes, political views or picking friends. But in many situations, we seek consistency: medicine, criminal justice, child custody decisions, economic forecasts, hiring, college admissions, fingerprint analysis or business choices about whether to greenlight a movie or consummate a merger.
Consistency equals fairness. If bias can be eliminated and sensible processes put in place, we should be able to arrive at the “right” result. Lack of consistency too often produces the wrong results because it’s often no better, the authors write, than the random judgments of “a dart-throwing chimpanzee.” And, of course, unexplained inconsistency undermines credibility and the systems in which those judgements are made.
As the authors explain in their introduction, a team of target shooters whose shots always fall to the right of the bull’s-eye is exhibiting a bias, as is a judge who always sentences Black people more harshly. That’s bad, but at least they are consistent, which means the biases can be identified and corrected. But another team whose shots are scattered in different directions away from the target is shooting noisily, and that’s harder to correct. A third team whose shots all go to the left of the bull’s-eye but are scattered high and low is both biased and noisy.
Despite its prominence in so many realms of human judgment, the authors note that “noise is rarely recognized,” let alone counteracted. Which is why the parade of noise examples that the authors provide are so compelling, and why gathering the examples in one place to demonstrate the cost of noise and then suggesting noise reduction techniques, or “decision hygiene,” makes this book so important. We are living in a moment of rampant polarization and distrust in the fundamental institutions that underpin civil society. Eradicating the noise that leads to random, unfair decisions will help us regain trust in one another.
“Noise” seems certain to make a mark by calling attention to the problem and providing a tangible guide to reducing it. Despite the authors’ intimidating academic credentials, they take pains to explain, even with welcome redundancy, their various categories of noise, the experiments and formulas that they introduce, as well as their conclusions and solutions.
Some decision hygiene is relatively easy. “Occasion noise” — the problem of a judge handing out stiffer sentences depending on whether a favorite sports team won or lost or whether it’s before or after lunch (yes, studies have found that, too) — can, like bias, be recognized during a “noise audit” and presumably dealt with. “System noise,” in which insurance adjusters, doctors, project planners or business strategists assess the same facts with that unfortunate variability, requires a more energetic decision hygiene.