Risk Savvy: How to Make Good Decisions

by Gerd Gigerenzer

The illusion of certainty has two faces. Whenever known risks are mistaken for absolute certainty, the zero-risk illusion occurs (Figure 2-4, left arrow). Modern technologies that many of us believe to be all but infallible, such as HIV tests, genetic analyses, and imaging tests, provide high-tech vehicles for illusory certainty. The calculable risk illusion (or turkey illusion; see below) is different. It mistakes uncertainty for known risks. Like the zero-risk illusion, it is shown as a move to the left-hand side in Figure 2-4 (right arrow). In both cases, there is a clash between the real world and the perceived one. Let’s begin with risks that are mistaken for certainty. Figure 2-4. Two kinds of illusions of certainty. The first is to confuse a world of risk with one of certainty—the zero-risk illusion. The second is to confuse a world of uncertainty with one of known risk—the turkey illusion (calculable-risk illusion). In each case, the illusion corresponds to an arrow moving from the right side to the left.