摘要：This paper introduces an axiomatic model of decision making where a person's subjective judgment as to the likelihood of different states of nature depends upon her anticipated payoff in those states. In the resulting representation the payoff consequences of an event affect beliefs as if they were part of the evidence about its likelihood. A parameter determines both the direction and weight of this `evidence', with positive values corresponding to optimism, and negative values to pessimism. Changes to the expected payoff consequences of an event amount to new `evidence', and can affect beliefs even in the absence of new information. The magnitude of the bias is greatest in situations that combine high stakes and great uncertainty, and is only indirectly related to the cost in poor decisions. If uncertainty cannot be readily reduced a substantial bias may remain regardless of its consequences. The model can account for a wide range of psychology evidence, including wishful thinking, cognitive dissonance, and unrealistic pessimism. Economic consequences are explored in various settings, such as the economics of crime, where increased punishment may fail to deter crime
