行为决策中模糊规避研究的回顾与展望

模糊规避是指在相同奖赏的情况下,决策者会偏好有精确概率的事件而不是从主观上判断具有相同模糊概率的事件。自从Ellsberg提出模糊规避的概念以来,模糊规避已在行为决策研究的多个领域得到广泛验证。本文梳理了近五十年来关于模糊规避的研究文献,系统分析了模糊规避的研究范式、心理机制和影响因素,同时提出了未来的研究展望。     

概率大小、损益结果和认知闭合需要对模糊规避的影响

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。本研究探讨了概率大小、损益结果和认知闭合需要对模糊规避的影响。研究发现,在小概率受益的情况下,个体倾向于模糊寻求;在中概率受益的情况下,个体倾向于模糊规避;在高概率受益的情况下,个体倾向于模糊规避;在小概率损失的情况下,个体倾向于模糊规避;在中概率损失的情况下,个体倾向于模糊规避;在高概率损失的情况下,个体倾向于模糊寻求。但是,研究并未发现认知闭合需要对模糊规避有预测作用。     

风险来源与决策:背信规避现象及人际联结需求的作用

经典的风险决策研究及相关理论模型关注人们如何对以不同概率出现的损益结果进行评价与选择,但很少区分和探究在相同概率和损益值下不同风险来源对决策的影响。事实上,决策情境中的风险既可能源自客观因素,也可能源自人为因素。与相同大小的客观风险相比,人们更规避人为风险,这种现象被称为"背信规避"。本研究采用信任博弈任务,通过最小可接受概率法和决策选择法两种方式探讨风险来源对决策冒险性的影响。结果发现:(1)中国被试存在"背信规避"现象,即对人为风险的规避程度高于客观风险;(2)当恐惧情绪被唤起时,被试对人为风险的规避程度降低,使得背信规避现象消失,甚至出现"反背信规避"倾向;(3)人际联结需求影响背信规避,人为风险下人际联结需求中介了恐惧情绪对决策冒险性的影响。上述结果有助于加深我们对风险来源影响决策的现象及其机制的理解。     

概率水平与模糊性对短视损失规避的影响

短视损失规避是指如果投资者频繁地评估其投资回报,那么他就会经常改变其投资决策,进而减少对风险资产的投入。本文采用实验法探讨了任务概率水平以及模糊性对短视损失规避的影响。结果发现短视损失规避只存在于中等损失概率任务中,说明该现象并非普遍存在;当概率模糊时,高损失概率任务中出现短视损失规避,而低损失概率任务中则出现反向的短视损失规避,说明模糊性能扩展“短视”起作用的概率范围。     

不确定性容忍度对模糊决策中决策偏好的影响及其情景依赖性*

研究以Ellsberg选瓶任务为决策材料,探讨了不同任务特征下个体不确定性容忍度对模糊决策中决策偏好的影响。结果发现,获益情景下:高概率时高、低容忍度个体对模糊选项的选择无显著差异,均偏好模糊规避;中概率时低容忍度个体比高容忍度个体表现出更低程度的模糊规避,前者倾向于模糊中立,后者倾向于模糊规避;低概率时两者对模糊选项的选择无显著差异,均倾向于模糊中立。损失情景下:高概率时两者对模糊选项的选择无显著差异,均倾向于模糊寻求;中概率时低容忍度比高容忍度个体更偏好模糊寻求,前者倾向于模糊寻求,后者倾向于模糊中立;低概率时两者对模糊选项的选择无显著差异,均倾向于模糊规避。这表明,不确定性容忍度对模糊决策偏好产生作用,但这种作用会受到损益概率和损益结果的影响,具有情景依赖性。     

应激对模糊决策的影响：认知和神经机制

模糊决策是指决策者无法预先知道结果发生的概率,只能依赖主观判断而进行的决策。应激会影响模糊决策,但不同研究结果并不一致,从模糊决策的认知成分入手能帮助我们更好地理解应激对模糊决策的影响。本研究从学习反馈、奖赏敏感性和风险偏好三个方面梳理了现有的行为和脑机制研究文献,发现应激对模糊决策的影响主要表现为应激导致反馈受阻、重赏轻罚、增加冒险三个方面。未来的研究应该关注应激类型和强度对模糊决策的不同影响,同时进一步拓展应激状态下模糊决策中认知与情绪的交互效应研究。     

模糊决策的情境依赖性

实验1采用艾尔斯伯格悖论的研究范式,探究被试对模糊的厌恶倾向以及在决策过程中所采用的决策策略。结果发现：被试对确定选项和模糊选项的选择存在差异;在肯定形式下倾向于确定选项,而在否定形式下则倾向于模糊选项,采用了利益最大化策略。实验2采用艾尔斯伯格悖论的变式,通过操纵概率和任务类型,发现：模糊决策具有情境依赖性,并非任何情况下个体都厌恶模糊。当风险选项不能满足自己的需要,即获胜机率比较小时,人们会偏向模糊选项。     

澳门人少涉赌是规避风险还是规避后悔？

是风险规避还是后悔规避左右人们的冒险行为？基于风险行为跨领域特殊性,本研究假设：决策者是规避风险还是规避后悔具有领域特异性。本研究选取有涉赌经验的澳门居民为样本,以其参与13种博彩的次数为指标考察其真实风险行为。结果验证了上述假设,风险规避说或后悔规避说都不能单独解释个体的风险倾向,个体是风险规避、后悔规避,或二者皆有,取决于其所处的具体风险情境类别。该发现有助于加深对风险行为特征的认识,亦可为预防及应对问题赌博提供启发和指导。     

主体关联性对贝叶斯推理概率估计的影响

用贝叶斯推理问题为实验材料,探讨了主体关联性对贝叶斯推理概率估计的影响。结果表明,当估计的事件与主体有关时,被试对消极事件概率估计较低,对积极事件概率估计值;当估计的事件与主体无关时,被试对消极事件和积极事件的概率估计无显著差异。反应时分析表明,被试对消极事件的概率估计比对积极事件的概率估计时间显著地长,当消极事件与主体有关时概率估计时间就更长;而对积极事件的概率估计,与主体有关和与主体无关时反应时差异不显著。这表明,被试对消极事件的概率估计(特别是消极事件与己有关时)更为慎重。     

从对框架效应的分析看风险决策的神经基础

对风险决策的研究近年来一直是微观经济学和心理学的热门,但是从传统的决策理论到主张有限理性的预期理论大多是对决策行为的研究,决策的心理机制一直是无法解释的黑箱子。令人兴奋的是近几年来神经科学家及其他领域的学者开始用先进的神经心理学的方法来研究风险决策,试图理解神经过程调节风险决策行为的方式。文章从分析违背“不变性”原则的框架效应入手,从正反框架、确定选择和风险选择、风险规避和风险寻求、高估小概率事件几个方面,全面分析风险决策可能的神经基础。在总结已有研究的基础上提出了把风险决策研究扩展到不确定决策,把风险决策中的一次决策研究扩展到多次决策的研究思路     

Ambiguity Aversion,Comparative Ignorance,and Decision Context

People typically find bets less attractive when the probability of receiving a prize is more vague or ambiguous (Ellsberg, 1961). According to Fox and Tversky's (1995) comparative ignorance hypothesis, ambiguity aversion is driven by the comparison with more familiar events or more knowledgeable individuals, and diminishes or disappears in the absence of such a comparison. In this paper we emphasize that “comparative ignorance” refers to the state of mind of the decision maker. We extend the comparative ignorance hypothesis by documenting four new ways in which decision context can affect willingness to act under uncertainty that do not rely on the comparative-noncomparative evaluation paradigm used in previous studies. First, people find uncertain bets more attractive when preceded by questions about less familiar items than when preceded by questions about more familiar items. Second, the preference to bet on more familiar domains is less pronounced for the first domain evaluated on a survey than for later domains. Third, people find bets less attractive when they are provided with diagnostic information that they do not know how to use, compared to when they are provided with no such information. Finally, people are sensitive to the relative competence of their counterpart when playing a simple competitive (matching pennies) game, but not when playing a noncompetitive (coordination) game that has the same mixed strategy Nash equilibrium.     

Attributions for ambiguity in a treatment-decision context can create ambiguity aversion or seeking

The phenomenon of ambiguity aversion suggests that people prefer options that offer precisely rather than imprecisely known chances of success. However, past work on people's responses to ambiguity in health treatment contexts found ambiguity seeking rather than aversion. The present work addressed whether such findings reflected a broad tendency for ambiguity seeking in health treatment contexts or whether specific attributions for ambiguity play a substantial role. In three studies, people choose between two treatment options that involved similar underlying probabilities, except that the probabilities for one option involved ambiguity. The attributions offered for the ambiguity played an important role in the results. For example, when the range of probabilities associated with an ambiguous treatment was attributed to the fact that different studies yield different results, participants tended to show ambiguity aversion or indifference. However, when the range was attributed to something that participants could control (e.g., regular application of a cream) or something about which they were overoptimistic (e.g., their immune system function), participants tended to show ambiguity seeking. Health professionals should be mindful of how people will interpret and use information about ambiguity when choosing among treatments.     

Impact of regulatory focus on ambiguity aversion

Although prior research has shown that some people prefer a risky to an ambiguous option, this study further proposes that people's regulatory focus (promotion vs. prevention) might influence their ambiguity aversion. Three experiments have tested whether people with promotion focus showed less ambiguity aversion than those with prevention focus: The first experiment revealed that, compared with chronically promotion‐focused individuals, prevention‐focused subjects preferred a risky to an ambiguous option. In the second experiment, priming of the subjects' goal orientations led to similar results. Experiment 3 demonstrated that participants showed less ambiguity aversion for the expected performance of an investment product representative of promotion (e.g., a stock fund) rather than one representative of prevention (e.g., a bond fund). In other words, people showed less preference for a bond fund when the probability distribution of its expected performance was unknown than when it was known, whereas they showed less preference difference between known and unknown probability distributions for the expected performance of a stock fund. This study has integrated research pertaining to regulatory focus and ambiguity aversion, and the results have confirmed that the impact of regulatory focus on ambiguity aversion is robust across different methods and decision tasks. Copyright © 2010 John Wiley & Sons, Ltd.     

Ambiguity Attitudes over Time

Previous research demonstrates that individuals exhibit a stronger level of ambiguity aversion for high probabilities than for low probabilities. Given that risky and ambiguous prospects are often unresolved until a future date (e.g., investment decisions, new product launches, and medical interventions), this study examines the impact of time on ambiguity preferences at different probability levels. Our experimental results indicate that although ambiguity preferences for low‐probability events remain constant, a robust effect of time occurs for high‐probability events. More specifically, temporal distance mitigates ambiguity aversion. This effect is consistent for different elicitation methods (preference rating and probability–ambiguity trade‐off tasks). We propose a dual‐process model (affective versus cognitive processing styles) to explain our results. Affective processing for high‐probability lotteries resolved in the current period increases ambiguity aversion, while cognitive processing leads to less ambiguity‐averse choices for future lotteries. Copyright © 2015 John Wiley & Sons, Ltd.     

Ambiguity attitudes in qualitative contexts: The role of prior beliefs

Most studies of ambiguity aversion rely on experimental paradigms involving monetary bets. Thus, the extent to which ambiguity aversion occurs outside of such contexts is much less understood, particularly when the situation cannot easily be reduced to numerical terms. The present work seeks to understand whether people prefer to avoid ambiguous decisions in a variety of different qualitative domains (e.g., work, family, love, friendship, exercise, study, and health), and, if so, to determine the role played by prior beliefs in those domains. Across three studies, we presented participants with 24 vignettes and measured the degree to which they preferred risk to ambiguity in each. We also asked them for their prior probability estimates about the likely outcomes in the ambiguous events. Ambiguity aversion was observed in the vast majority of vignettes, but at different magnitudes. It was predicted by whether the vignette involved gain or loss as well as by people's prior beliefs; however, the heterogeneity between people meant that the role of prior beliefs was only evident in an individual-level analysis (i.e., not at the group level). Our results suggest that the desire to avoid ambiguity occurs in a wide variety of qualitative contexts but to different degrees for different people and may be partially driven by unfavorable prior estimates of the likely outcomes of the ambiguous events.     

Robust Tolerance for Ambiguity

We argue first that "ambiguous prospects" should be defined in a way that is compatible with dictionary definitions and other technical uses of ambiguity. We then define an ambiguous prospect as a disjunction of risky prospects. Then to harmonize some findings in the literature we test the hypothesis that people are ambiguity indifferent up to moderate amounts of ambiguity and are ambiguity averse only for large amounts of ambiguity. To test the hypothesis we found probability equivalents to risk for prospects of varying degrees of ambiguity. Up to an ambiguity range of .7 the equivalents were near that of a normatively equivalent risky prospect while the equivalents of highly ambiguous prospects differed. We interpret the data in terms of competing desires for minimum effort and maximum accuracy.     

Protecting Against Low‐Probability Disasters: The Role of Worry

We carry out a large monetary stakes insurance experiment with very small probabilities of losses and ambiguous as well as exact probabilities. Many individuals do not want to pay anything for insurance whether the probabilities are given exactly or are ambiguous. Many others, however, are willing to pay surprisingly large amounts. With ambiguity, the percentage of those paying nothing is smaller and the willingness to pay (WTP) of the other individuals larger than with exact probabilities. Comparing elasticities with ambiguity, we find that worry is much more important than subjective probability in determining WTP for insurance. Furthermore, when the ambiguous loss probability is increased by a factor of 1000, it has almost no effect on WTP. Copyright © 2011 John Wiley & Sons, Ltd.