|Alternative Title||Is Intertemporal Decision-Making Based on a Temporal Discounting Process? Evidence from Process Testing|
|Thesis Advisor||李纾 ; 梁竹苑|
|Place of Conferral||北京|
|Keyword||跨期决策 延迟折扣计算 眼动追踪 脑功能连接 眼动轨迹分析|
研究一使用认知行为实验，旨在检验新实验范式的有效性。研究一发现：1)基线折扣任务的任务表现上符合折扣计算假设的预测：在反应时上，低难度条件下，基线折扣任务的反应时要短于高难度条件；在正确率上，基线折扣任务的正确率受到计算难度和计算能力的影响，计算难度越低，计算能力越高，正确率越高。2) 自主跨期决策任务的的任务表现与基线折扣任务不同：自主跨期任务的反应时短于基线折扣任务；且其选择偏好(选择SS 选项的比例)受选项结果大小的影响：结果越大，选择SS 选项的比例越少。此外，小结果条件下被试越倾向于基于直觉(直觉的认知反思风格分数越高)，选择SS 选项的比例越大。研究一的结果表明，研究所设计的新实验范式在检验折扣计算假设中有效，且从任务表现层面看，自主跨期任务并不符合折扣计算假设的预测。
务中分配在 LL 选项上的注视点个数更多，且分配在 LL 选项中的结果或时间上的注视点个数，均比SS 选项结果更多。但在基线折扣任务中没有此效应。研究二的结果表明，本研究设计的实验任务范式有效并可靠，从眼动特征层面上看，自主跨期任务并不符合折扣计算假设的预测，而是符合齐当别模型的预测。
|Other Abstract||Intertemporal choice refers to the tradeoff among outcomes that occur at different time points. It covers a wide range of topics at individual and national levels, from daily trivial, including personal health and wealth, to developmental issues that concern the future prosperity of a country. Current studies have different findings about the basic theoretical models of intertemporal choice. The family of discounting and non-discounting models is proposed based on unbounded rationality and bounded rationality, respectively. These models disagree on whether intertemporal choice is based on discounting calculation. Previous studies could well predict decision results through testing methods that are based on outcomes, such as result prediction and model fitting. However, the decision process remains unknown. The methods and techniques (e.g., eye tracking and fMRI) of process testing can be applied to explore directly the cognitive process of decision making, and thus they can also be used to solve this contradiction. Thus, this study aims to determine whether intertemporal choice is based on discounting calculation by using process testing methods.|
A new set of experimental paradigm is designed. The design includes two experimental tasks, namely, the baseline discounting task and the free intertemporal choice task. The former task is in line with the hypothesis of discounting calculation, and the subjects in the latter task make intertemporal choice on their own. Based on the basic logic of double dissociation, this study chooses manipulated variables and moderator variables that only affect baseline discounting task or free intertemporal choice task. Manipulated variables cover the effect of attribute of stimuli on these two tasks, including computational difficulty and outcome magnitude of each option, respectively. Moderator variables cover cognitive ability and personality traits which were correlated with these two tasks, including computational ability and maximization preference, and cognitive style and impulsive personality, respectively.
Study 1 aims to test the validity of the new experimental paradigm through cognitive behavioral experiment. The results of Study 1 are as follows. First, the behavioral performance of discounting baseline task met the prediction of discounting calculation hypothesis. In terms of reaction time, the baseline discounting task exhibited shorter reaction time under low difficulty condition than high difficulty condition. In terms of accuracy, the task was influenced by computational difficulty and computational ability. High computational ability and low computational difficulty resulted in high accuracy. Second, the performance of the free intertemporal choice task was different from that of the baseline discounting task, i.e., the reaction time of intertemporal choice task was shorter than that of baseline discounting task. Its choice of preference (the percentage of choosing the SS option) was influenced by outcome magnitude. Specifically, large magnitude of outcome results in less percentage in choosing the SS option. Moreover, subjects were more inclined to choose based on intuition (high score on intuition in the cognitive style test) under small outcome magnitude condition, which results in greater percentage in choosing the SS option. Results of Study 1 indicate that the new experimental paradigm is effective in testing the hypothesis of discounting calculation. Based on task performance, the free intertemporal choice task did not meet the prediction of
discounting calculation hypothesis.
Study 2 aims to provide process testing evidence to the assumption of discounting calculation by using eye tracking technique. This study also explores whether the eye tracking characteristics of intertemporal choice meet the prediction of equate-to-differentiate model, which is a non-discounting model. Study 2 obtained the following results. First, the behavioral results accorded with those of Study 1. Second, in terms of processing depth, the baseline discounting task met the hypothesis of discounting calculation, in contrast to the free intertemporal choice. The average fixation duration of the baseline discounting task was longer than the free intertemporal choice task, and was positively correlated with computational difficulty. Third, in terms of scanpath similarity, the two tasks had different cognitive processes; the within-task similarity score was higher than the between-task similarity score. Fourth, the attention allocation of free intertemporal choice task met the prediction of equate-to-differentiate model; the larger the outcome magnitude was, the more fixation number fell in LL option in the free intertemporal choice task, instead of in SS option. The number of fixation in the outcome or time of LL option was higher than that of SS option. The baseline discounting task did not show this pattern. Results from Study 2 indicate that the experiment paradigm is valid and reliable. Based on the eye movement perspective, the free intertemporal choice task met the prediction of equate-to-differentiate model, but not the discounting calculation hypothesis.
Study 3 aims to provide neuroimaging evidence in testing intertemporal choice discounting process and to verify whether the brain activity pattern of free intertemporal choice meets the prediction of the equate-to-differentiate model. Study 3 obtained the following findings. First, the behavioral results agree with those in Studies 1 and 2. Second, in terms of brain activity and functional connectivity, the baseline discounting task accorded with the discounting calculation hypothesis, whereas the free intertemporal choice task did not. Specifically, for in the function connectivity between the inferior frontal gyrus (representing time) and the inferior parietal sulcus (representing value) in the baseline discounting task, computational difficult resulted in strong function connectivities. This effect was not observed in the free intertemporal choice task. In the baseline discounting task, the activities of brain areas that are associated with calculation, including putamen, left inferior frontal gyrus, and bilateral precuneus, were stronger with increasing computational difficulty. However, the outcome magnitude did not affect the brain activities of baseline discounting task. Third, the brain activity of free intertemporal choice met the prediction of equate-to-differentiate model better. The activities of the left dorsolateral prefrontal cortex and the bilateral precuneus (representing cognitive control and decision conflicts) were stronger with increasing option outcomes. However, computational difficulty did not affect the brain activity of free intertemporal choice task. Results from Study 3 indicate that, based on the brain activity perspective, the free intertemporal choice task better met the prediction of equate-to-differentiate model, but not the discounting calculation hypothesis.
In summary, this study designed and tested a new experimental paradigm, and integrated behavioral, eye tracking, and fMRI evidences based on the logic of double dissociation to test the discounting calculation hypothesis. The obtained results verified that the intertemporal choice does not follow the discounting calculation process of discounting family model through the new experimental paradigm. Instead, the process of intertemporal choice better fit the equate-to-differentiate model. Results of this study indicate that process testing methods are suitable for testing theoretical models of intertemporal choice. This study sheds light on the methodologies to better answer the question of “how people make intertemporal choice” while providing practical evidence at multiple levels.
|张阳阳. 跨期决策是否基于“折扣计算”:来自过程检验的证据[D]. 北京. 中国科学院研究生院,2016.|
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