ABSTRACT
The influence of prior belief on reasoning and decision making has perhaps produced more experimental investigations, more claims of bias, and more arguments about human rationality than any other single issue. There are three substantial cognitive literatures concerned with this issue, which we will examine in some detail in this chapter, namely:
The use or neglect of prior probabilities in tasks designed as tests of Bayesian decision making. Most famously, this literature includes a claim that information about base rates is grossly neglected when subjects make posterior probability judgements in the light of specific evidence.
Confirmation bias—which is defined as a tendency to seek information that will confirm rather than falsify existing beliefs, theories, and hypotheses. Evidence for confirmation bias is adduced from work within several different paradigms and traditions.
Belief bias—which is an effect studied in the deductive reasoning literature and consists of a tendency for people to judge the validity of an argument on the basis of the prior believability of its conclusion.
