健康与遗传心理学研究室知识库

跨期选择是行为决策领域中的一个基本概念，指当结果发生在不同时间点时，人们对这些结果做出的权衡取舍。在现实生活中，人们做出的很多重要决策均涉及跨期选择。通过两个研究，本文从行为和神经基础的层面探讨了跨期选择的机制。

研究一关注现实生活中的一种重要的跨期选择:养老金决策。研究一以中国劳务输出工人为被试，在真实情境中探讨了时间折扣偏差及其他相关因素对养老金决策的影响作用。通过调查问卷及养老金购买行为记录，我们发现，被试表现出一种反转的、行为上的养老金谜题:少数被试有购买养老金意愿，但多数被试最终实际参抓!了养老金计划。同时，在控制了离职意愿的影响后，我们发现，可预测购买养老金意愿及行为的变量不同:保险相关经验可预测养老金购买意愿，但养老金购买行为可由时间折扣率和定期储蓄率预测。这一结果将对更好地设计和推广养老金计划起到理论指导作用。

在研究二中，基于以往行为研究发现的符号效应，即获得情境的时间折扣率高于损失情境，我们使用事件相关的功能磁共振成像技术一，探索了跨期选择中时间折扣的神经机制。研究二使用了两个跨期选择的决策任务:获得和损失情境的跨期选择任务，且两个任务的形式完全对称。研究结果发现，当被试对一未来的获得与损失进行选择时，侧额p_卜和后顶叶区域都发生了激活，但在折扣损失时，不仅这两个区域的脑激活更强，脑岛、丘脑、背侧纹状体等区域也显著激活;而如果被试需要对即刻的选项进行选择，后扣带回和内侧前额叶皮质都会发生激活，但在折扣损失时，前扣带回、脑岛和额上回都会发生激活。这些结果说明，人类的大脑对未来损失比对未来的获得更加敏感，而这可能是由诸如恐惧、厌恶之类的负性情绪所驱动的。

本文的主要结论是:(1)购买养老金存在意愿小于行为的现象，且时间折扣率可预测养老金决策的比率;(2)额顶网络参与获得与损失情境中的时间折扣过程，但是损失条件下时一间折扣的神经机制与获得条件下并不对称。

Intertemporal choice is the tradeoff among outcomes occurring at different points in time, which is a basic concept in behavior decision making field and relate to many important decisions in the real worlds The present research explored the mechanism of interternporal choice from two levels: behavior and neural mechanism by two studies.

The first study focused on the annuity decision, one type of intertemporal choice in the real world. In a field context, we explored the potential effect of time discounting biases to the annuity puzzle and other related factors. The results suggest that participants showed the reversed behavioral annuity puzzles: few individuals intended to purchase annuities, while more individuals actually joined annuity program. Moreover, after excluding the influence of job-quit intention, this behavioral annuity puzzle can be predicted by different factors: for annuity intention, the best predictors are insurance related experiences, whereas for annuity purchasing decision or annuity behavior, are time discounting rate and demand saving rates.

In the second research, using event-related functional magnetic resonance imaging, we comprehensively investigated the neural mechanism of temporal discounting using two decision-making tasks with a symmetric pattern of gains and losses. Our results revealed that the lateral prefrontal and posterior parietal areas were activated in discounting both future gains and future losses, but their activations were stronger when discounting losses, Moreover, we found that the insula, thalamus and dorsal striatum were more activated during intertemporal choices involving losses, suggesting that the enhanced sensitivity to losses may be driven by negative emotions. In addition, whereas the posterior cingulate cortex and medial prefrontal cortex were activated when the choices included immediate options, extra regions including the anterior cingulate cortex, insula and superior frontal gyrus were preferentially activated when the choices involved immediate losses.

Taken together， our findings suggest that (1) the decrease in tune discounting rates could lead to increase in the annuitization rate; (2) a fronto-parietal. network supports the common discounting process, and more importantly, discounting future losses and gains occurs asymmetrically in the brain.

We also discussed the implications for research on annuity and intertemporal decision making, as well as for the annuity design and promotion in real world are discussed. Moreover, we speculated that the results may provide a neural basis for the phenomenon that future losses are discounted less steeply than future gains.