Noise: A Flaw in Human Judgment

by Daniel Kahneman

In general, we jump to conclusions, then stick to them. We think we base our opinions on evidence, but the evidence we consider and our interpretation of it are likely to be distorted, at least to some extent, to fit our initial snap judgment. As a result, we maintain the coherence of the overall story that has emerged in our mind. This process is fine, of course, if the conclusions are correct. When the initial evaluation is erroneous, however, the tendency to stick to it in the face of contradictory evidence is likely to amplify errors. And this effect is difficult to control, because information that we have heard or seen is impossible to ignore and often difficult to forget. In court, judges sometimes instruct jurors to disregard an inadmissible piece of evidence they have heard, but this is not a realistic instruction (although it may be helpful in jury deliberation, where arguments explicitly based on this evidence can be rejected).