模糊规避的形成机制:基于可评价性假设的视角

The Formation Mechanism of Ambiguity Aversion:A Perspective Based on the Evaluability Hypothesis

模糊规避是指在相同奖赏的情况下,决策者会力图规避从主观上判断具有模糊概率的事件而偏好具有相同精确概率的事件。本研究使用同时评价、单独评价的研究范式从随机事件和自然事件两个领域来探讨模糊规避的形成机制。研究结果表明,当风险事件和模糊事件同时评价时,个体倾向于模糊规避;当风险事件和模糊事件单独评价时,模糊规避会消失。

Ambiguity aversion refers to the phenomenon that people prefer events with known probabilities to similar ambiguous events in which the decision maker does not know the values of the probabilities. Since ambiguity aversion was proposed by Ellsberg in 1961, there have been three main models accounting for ambiguity aversion： the other evaluation hypothesis, the competence hypothesis and the comparative ignorance hypothesis. The other evaluation hypothesis suggests that increasing the number of people watching a decision enhances ambiguity aversion, and enhances it more than other factors that researchers manipulate.The competence hypothesis suggests that people prefer betting on their own judgment to an equiprobable chance event only when they consider themselves knowledgeable, but not otherwise. The comparative ignorance hypothesis suggests that ambiguity aversion increases with the perception that others are more competent and more knowledgeable. To investigate the influence of joint evaluation and separate evaluation on individuals’ ambiguity aversion, a 2 （ambiguous event vs. risky event） ×2 （ joint evaluation vs. separate evaluation） mixed experimental design was adopted. In the 1first experiment, the subjects were required to indicate their WTP of ambiguous events and risky events. In the 2nd experiment, every piece of experimental episode consisted of ＂below＂ and ＂not below＂ conditions under which the subjects were required to indicate their WTP. The research revealed that there was no significant difference in WTP between ambiguous events and risky events when evaluated simultaneously, when they were separately evaluated, there was a significant difference in WTP between ambiguous events and risky events. The results indicate that, when risky events and ambiguous events are evaluated simultaneously, people opt for ambiguity aversion; in case of a separate evaluation, however, ambiguity aversion will disappear.