Summary

Tversky and Kahneman describe some of their investigations where practical decision makers could use heuristics when they work in their own fields of expertise. But most investigations present laboratory type problems on probability to ordinary students. Tversky and Kahneman attribute the errors that the students make to their use of heuristics. But there are many other reasons for errors: failing to know the appropriate normative rules or failing to use them; problem questions that are too difficult for ordinary students to answer correctly; questions with misleading contexts; and the simple biases that occur in quantifying judgments. One student may fail for one reason whereas other students fail for other reasons. Training reduces the errors. Some of the original investigations now require changes of interpretation. One investigation shows how results that violate the representativeness heuristic can be accounted for by chanaging the dimension along which representativeness is judged.

Heuristics as substitutes for normative rules

During the 14 years between 1969 and 1983, Tversky and Kahneman publish numerous articles that introduce and develop their novel theory of the use of heuristic biases or rules of thumb in dealing with probabilities. In this book the biases are discussed in separate chapters. They are listed in Table 1.1, together with 2 additional biases described by Lichtenstein and Fischhoff or by Fischhoff, apparent overconfidence and hindsight bias. This work has had a major influence on theories of judgment and decision making.