Choice without Beliefs

9514908 EASLEY这个项目研究了以下重要问题：当一个人面临一个新的潜在的复杂的随机决策问题时，他会做什么？根据标准的期望效用理论，在做出任何选择之前，个体确定可能驱动世界状态的所有可能的随机过程，并访问这些过程的先验。尽管这一理论在相对简单的情况下很有吸引力，在这种情况下不需要进一步学习，但在复杂的情况下很难接受。该项目为静态期望效用最大化开发了另一种进化基础。在这个可供选择的框架内，个体并不能获得对所有可能的随机过程的信念。他们甚至不会尝试确定一组可能的过程。相反，他们会采取行动，并从自己的经验中学习。这里，个体从一组候选决策规则开始，从这些规则上的权重开始，并使用这些权重作为概率来选择初始规则。然后，她/他根据所选规则提出的建议行事。在观察到状态和所获得的回报之后，个体使用进化动态来更新规则的权重。他/她根据这些更新的权重选择在下一个日期使用的规则，依此类推。基于到目前为止已完成的工作，我们知道，在动力学上有三个自然公理：对称性、单调性和独立性，个体最终选择的规则是具有正确预期的主观期望效用最大化。该项目的一个部分是确定这些公理是否对这一结论是最小的。该项目将面向过程的选择模型扩展到更丰富的环境，并分析多个进化个体之间的相互作用。

9514908 Easley This project studies the following important question: What does an individual do when confronted with a new potentially complex, stochastic decision problem? According to standard expected utility theory, before making any choices the individual determines all possible stochastic processes that could be driving the states of the world and accesses a prior over these processes. As appealing as this theory is in relatively simple settings in which no further learning need occur, it is difficult to accept in complex settings. This project develops an alternative evolutionary foundation for static expected utility maximization. Within this alternative framework individuals do not access beliefs over all possible stochastic processes. They do not even attempt to determine the set of possible processes. Instead, they act and learn from their experience. Here an individual begins with a set of candidate decision rules, starts with weights on these rules, and selects an initial rule using these weights as probabilities. She/he then acts according to the recommendation made by the selected rule. After observing the state and the payoff that is achieved, the individual updates the weights on rules using an evolutionary dynamic. He/she selects the rule to use at the next date based on these updated weights, and so on. Based on the work completed so far, it is known that with three natural axioms on the dynamic: symmetry, monotonicity, and independence, the individual eventually chooses a rule that is a subjective expected utility maximizer with correct expectations. One part of the project is to determine if these axioms are minimal for this conclusion. This project extends the process oriented model of choice to richer settings and an analysis of interaction between multiple evolutionary individuals.