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Alternative TitleCompensatory Rule or Non-compensatory Rule: Neural Basis of Decision Making Under Risk
Thesis Advisor李纾
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline心理学
Keyword风险决策 补偿性规则 非补偿性规则 事件相关电位 功能磁共振成像
Abstract“人类在风险条件下如何做出判断和决策”是富有前景和重要意义的科学难题。在百余年的发展历程中,涌现出了许多自认为不同的风险决策理论,但目前占主导的期望法则家族理论实际上都只认同一种决策规则——补偿性规则(compensatory rule)。即认为在风险决策时需要通过加权求和的补偿性过程解决各选项相互不占优的决策冲突。但强调生态理性的启发式决策理论对这一共识提出了有力质疑,认为人们实际风险决策的过程更符合非补偿性规则,即一个维度上的缺陷并不能被另外一个维度上的优势所补偿。本论文综合运用神经科学、心理学、经济学的实验方法和技术手段,围绕补偿性-非补偿性规则的计算特征假设和冲突反应假设,探析风险决策的行为与神经机制。 研究1采用事件相关电位(event-related potential, ERP)的研究手段,从决策过程层面针对补偿性-非补偿性规则的计算特征假设,即,决策者的实际偏好选择过程若遵循补偿性规则,则对选项进行加权求和的计算难度将影响其决策过程;若遵循非补偿性规则,则对选项进行加权求和的计算难度将不会影响其决策过程。ERP结果表明,在偏好决策任务和期望价值任务中表现出双分离效应:影响补偿性过程的计算难度,只影响了期望价值决策任务中慢波的波幅,而对偏好决策任务无影响;相反,对启发式过程有影响的最小获益差异值,只有在偏好决策任务中影响了P300和慢波的波幅。这表明,偏好决策中并不存在补偿性规则所假设的计算过程。 研究2采用功能性磁共振成像技术(functional magnetic resonance imaging, fMRI),通过考察脑活动及其与行为指标相关性,检验补偿性-非补偿性规则的冲突反应假设,即,决策者的实际偏好选择过程若遵循补偿性规则,选项间的总效用值越接近,冲突越大;若遵循非补偿性规则,概率维度内差异值和可能结果维度内差异值越大,冲突越大。结果表明,在判断决策任务中,总效用差异值越小,被试的选择越均衡(即,越接近一半的被试选择单个选项),表明被试体验到的冲突越大;而在偏好决策任务中,概率/报酬维度差异值越达,被试的选择越均衡,冲突越大;与决策冲突相关的背内侧前额叶的激活水平在判断决策任务中随着总效用差异值的增加而降低,但是在偏好决策任务中随着概率/报酬维度差异值的增加而增加;背内侧前额叶的激活水平在偏好决策任务中强于判断决策任务。这些结果表明,偏好决策的冲突反应模式与判断决策不相同,偏好决策可能并不是一个纯粹的补偿性过程。 研究3采用功能性磁共振成像技术,通过对不同任务下脑活动的考察,检验补偿性规则在何种情境下更适用。结果表明,在单次决策任务中,相比于P bet条件,在$ bet条件中腹内侧前额叶和后扣带的激活水平更强。而在期望价值决策中,腹内侧前额叶和后扣带的激活水平呈现出相反的模式。在多次决策中,风险选项类型对腹内侧前额叶和后扣带激活水平的影响存在显著的个体差异。表现为行为结果与单次决策越一致的被试,表现出与单次决策中越一致的脑活动模式。这些结果表明,个体在单次决策和期望价值决策所使用的策略是不同的。在多次决策中个体的策略偏好存在个体差异,有些个体多次决策时采用与单次决策一致的策略,有些个体在多次决策时采用与期望价值理论较一致的策略。相比于单次决策而言,期望价值理论确实在多次决策中更适用。 总之,本论文结合行为学和认知神经研究的发现,表明风险决策并不遵循补偿性规则,为回答“风险决策的基本规则是什么”这一问题提供行为和神经水平的理论基础和实证证据。
Other AbstractUnderstanding how human minds make decisions under risk is a promising and important target for basic scientific research. The dominant theories about risky decision-making assume that decision conflicts are solved by a compensatory process involving a trade-off of probability against payoff, but it is unclear whether these theories actually represent the events that occur when people make a risky decision. Researchers have argued that an individual’s preferential choice can be better described by a non-compensatory process. Based on the computation and conflict hypotheses, the present thesis utilized psychological, neural and economic methods of research and analysis to explore the behavioral and neural mechanisms underlying risky decision-making. In Study 1, by using event-related potentials, we investigated the neurocognitive mechanisms underlying risky choice by contrasting a preferential choice task with an expected value choice task. The ERP data revealed that 1) the computational difficulty, which would be expected to influence a compensatory process, affected the slow wave only when participants were forced to choose the option with the highest expectation; and that 2) the difference in the minimum gains, which would be expected to be influential in a heuristic process, affected the P300 and slow wave when participants were asked to choose the preferred option. Our findings provide neural evidence that preferential choice is not based on an expectation computation and thus raised the question of whether expectation theories can provide an adequate description of individual risky decisions. In Study 2, by contrasting a preferential choice with a judgment-based choice that required a compensatory process using functional magnetic resonance imaging (fMRI), we explored the mechanisms underlying risky decision-making. First, using parametric analyses, we identified the dorsomedial prefrontal cortex (dMPFC) as the specific region in charge of task-related conflict in risky decision-making tasks. We also showed that the dMPFC was activated less when judgment-based choices were being made, implying that the conflict experienced during a judgment-based choice was not as strong as the conflict that was experienced during the preferential choice. Our results provide neural evidence that preferential choice cannot be characterized solely as a compensatory process. Thus, questions were raised about whether existing compensatory theories could adequately describe individual risky decisions. In Study 3, we conducted an fMRI study to explore whether there were separate neural mechanisms for short-run and long-run probabilistic events. We found that vMPFC and PCC were activated less in the P bet condition than the $ bet condition in the single-play preferential choice task, but reverse in the expected value choice task. We also found individual difference in the multiple-play preferential choice task. Overall result implied that the compensatory rule is more compelling in multiple-play situations. In sum, our results provide behavioral and neural evidence that preferential choice cannot be characterized solely as a compensatory process. We hope our findings could potentially lead to a better understanding of the underlying mechanism of risky decision-making, which could present important directions for future research.
Subject Area应用心理学
Document Type学位论文
Recommended Citation
GB/T 7714
饶俪琳. 补偿性还是非补偿性规则:探析风险决策的神经机制[D]. 北京. 中国科学院研究生院,2012.
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