Much psychological research in the last two decades has demonstrated that human responses deviate from the performance deemed normative according to various standard models of reasoning,judgment and decision making (e.g.,the basic axioms of logic,probability and utility theory) and show systematical cognitive biases. There are different interpretations of the gap between the normative and the descriptive behaviors,and conflicting viewpoints on whether these cognitive biases indicate systematic irrationalities in human cognition. The pessimists believe that the systematical cognitive biases mean normative defects in human thinking. The optimists,however,try to defend the assumption that human behavior and cognition is largely rational by appealing to the arguments of divergent task construal made by the experimenter and participants,the wrong norm being applied by the experimenter and the weak external validity of experimental studies. The dual rationality theory distinguishes personal rationality and impersonal rationality,and attempts to resolve the contradiction between the views of the pessimists and the optimists.%当代认知心理学研究发现，人们的推理、判断和决策行为常常偏离形式逻辑、概率和决策理论等规范原理，表现出系统的认知偏差。研究者对认知偏差及其实验研究的不同理解引发了一场持续至今的关于人类理性的争论。悲观论者认为系统认知偏差意味着人们的思维能力存在规范性缺陷，认知偏差研究为人类理性提供了否证性证据。乐观论者从理解问题、规范理论问题和外部效度问题等方面为人类理性进行辩护。两种理性观则把人类理性区分为个人取向与非个人取向两种，试图消解悲观论和乐观论之间的矛盾。
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