认知与发展心理学研究室知识库

延迟折扣是自我控制的重要指标，主要指个体在面对大的延迟奖赏和小的即时奖赏时，更偏好后者。同时它也是冲动控制的重要指标。冲动障碍，比如赌博、成瘾等障碍，均与延迟折扣有重要关系。研究发现，青少年时期个体的延迟折扣情况可以预测他们成年后的工作成就、生活满意度等。因此，研究儿童、青少年的延迟折扣行为，意义重大。

对于延迟折扣行为的解释，双系统理论认为，包括前额和顶叶等在内的认知系统与包括中脑边缘多巴胺和边缘奖赏区域等在内的奖赏系统，对延迟折扣选择起决定作用。金钱作为常用的延迟折扣奖赏材料，在双系统中，是否有别于其他奖赏材料，值得探讨。从神经活动随时间进程角度，儿童、青少年在金钱延迟折扣中，认知系统和奖赏系统的表现如何，有必要深入探讨。对于青少年，他们的奖赏系统和认知系统发展差异较大，且大脑发育模块化还在继续，他们的认知系统和奖赏系统如何受到认知因素和奖赏因素的影响，目前尚不清楚。为此，设计了如下研究： 研究包含行为和脑电层面的探讨。研究一选取大学生成人被试，采用金钱、食物延迟折扣任务，旨在探讨金钱、食物的双系统表现差异。研究二选取 9-10 岁儿童、15 岁左右的青少年、大学生成人被试，采用金钱延迟折扣任务，旨在探讨儿童、青少年的金钱延迟折扣的双系统特点。研究三、四、五选取 15 岁左右的青少年、大学生成人被试。研究三采用工作记忆任务(2-back)、抑制任务(数字stroop 任务)、改编的金钱延迟折扣任务，旨在探讨认知因素对青少年延迟折扣的影响。研究四采用 MID(Monetary incentive delay)任务 、改编的金钱延迟折扣任务，旨在探讨奖赏的不同阶段对青少年延迟折扣的影响。研究五，综合考察认知、奖赏对青少年延迟折扣的影响。研究结果表明：

(1) 与食物相比，金钱任务中，个体更偏爱延迟奖赏；神经活动上，金钱与食物的主要差异体现在认知系统(N2 成分)；对 P3 成分，女生在金钱和零食上存在差异，男生没有。

(2) 儿童、青少年在奖赏系统中(P2 成分)表现出加工速度滞后的特点，在认知系统中(N2 成分)表现出不成熟。N2 成分中，儿童、青少年都表现出波幅更小的特点。P3 成分(部分属于奖赏系统，部分属于认知系统)中，儿童的波幅比成人更大、潜伏期更短；青少年的潜伏期比成人更长，波幅与成人无差异。体现出儿童、青少年在认知系统、奖赏系统中不同的滞后表现。

(3) 对青少年，工作记忆资源多时，抑制能力越强，个体越偏爱延迟奖赏；而对成人，工作记忆能力强时，抑制能力越弱，个体越偏爱延迟奖赏。体现了青少年和成人的认知系统对延迟折扣的不同影响。

(4) 对青少年，仅奖赏反馈阶段的加工过程可以预测他们的延迟折扣行为，而对成人，动机和反馈阶段的加工过程皆可以预测他们的延迟折扣行为。此外，反馈阶段，对青少年，早期结果评估可以预测他们的延迟折扣行为，晚期结果评估不能；对成人而言，早期结果评估和晚期结果评估都能预测他们的延迟折扣行为。

(5) 在金钱延迟折扣任务中，青少年的工作记忆与奖赏的交互作用能够显著预测青少年的延迟折扣行为，具体表现为，青少年的工作记忆的加工进程较早时，奖赏加工越敏感，越偏爱延迟奖赏。体现认知和奖赏系统存在交互作用。

综上，本研究证实，延迟折扣任务中，金钱的双系统与食物的双系统存在差异。同时，本研究发现儿童、青少年在金钱延迟折扣任务中的双系统表现，丰富了双系统理论在发展中的运用。并且，本研究揭示了认知系统、奖赏系统在青少年和成人中的不同内在作用机制，不仅对双系统的内在加工过程进行了深入探讨，也为未来对青少年延迟折扣行为进行干预提供了新的视角和理论支持。

Delay discounting is an important indicator of self-control. It mainly refers to that individuals prefer large delayed rewards to small immediate rewards. At the same time, it is also an important indicator of impulse control. Impulse disorders, such as gambling and addiction, have an important relationship with delay discounting. Previous studies found that delay discounting in adolescents could predict their work achievement and life satisfaction in adulthood. Therefore, it is of great significance to study delay discounting behaviors of developing individuals.

For the explanation of delay discounting, the two-system theory suggests that the cognitive system including the frontal and parietal lobes and the reward system including the mesolimbic dopamine and limbic reward regions play crucial roles in delay discounting choices. It is worth exploring whether money as a kind of commonly used delay discounting reward is different from other reward materials in dual-system. From the perspective of neural activity over time, it is worth exploring the features of cognitive system and reward system in children and adolescents in monetary delay discounting. For adolescents, the development of their reward system and cognitive system is very different, and the modular segregation of the developing brain is still continuing. How their cognitive system and reward system are affected by cognitive factors and reward factors is unclear. To this end, the following studies are designed to investigate:

The studies involved behavioral and electrical aspects. In Study 1, adult college students were recruited to study the differences of dual-system features between monetary and food delay discounting tasks. In Study2, children aged 9-10, adolescents aged about 15 and college students were recruited to study the dual-system characteristics of monetary delay discounting in children and adolescents. Studies 3, 4 and 5 included adolescents aged about 15 and adults. In Study 3, the 2-back task, the digital Stroop task and the modified delay discounting task were used to explore the effects of cognitive factors on delay discounting among adolescents. Study 4 adopts the monetary incentive delay (MID) task and the modified delay discounting task to explore the effect of different reward stages on adolescents' delay discounting choices. In Study 5, the effects of cognition and reward on delay discounting were investigated. The results indicated that:

(1) Individuals preferred delayed monetary rewards more than food rewards in behavior. The main difference in neural activity between money and food was in the cognitive system (N2 component). About P3 component, there were differences between money and snacks for girls, but not for boys.

(2) Children and adolescents showed delayed processing speed in the reward system (P2 component) and immaturity in the cognitive system (N2 component). The amplitude of N2 component was smaller in both children and adolescents. For P3 component, which belongs to part of the reward system and part of the cognitive system, the P3 amplitude of children was larger than that of adults and the P3 latency is shorter. The P3 latency of adolescents was longer than that of adults, and theP3 amplitude was not different from that of adults. The results reflected the different lag performances of children and adolescents in cognitive system and reward system.

(3) For adolescents, when the working memory resource was in high level, the stronger the inhibition ability, the more delayed rewards adolescents would prefer. For adults, when the working memory ability was in high level, the weaker the inhibition ability, the more delayed rewards adults would prefer. It reflected the different effects of adolescents’ and adults’ cognitive systems on delay discounting.

(4) For adolescents, only the reward feedback stage could predict their delay discounting behavior, while for adults, both the motivation and feedback stage could predict their delay discounting behavior. In addition, in the feedback stage, for adolescents, the early outcome assessment could predict their delayed discounting behavior, but the late outcome assessment could not. For adults, both the early outcome assessment and the late outcome assessment could predict their delay discounting behavior.

(5) In the monetary delay discounting task, the interaction between working memory and reward sensitivity significantly predicted the delay discounting behavior of adolescents. Specifically, when the working memory processing was early, the more sensitive the reward processing, the more delayed rewards adolescents would prefer. It showed the interaction between the cognitive system and reward system.

Taken together, in delay discounting task, the dual systems for money were different from the dual systems for food. At the same time, this study discovered the dual-system features of children and adolescents in the monetary delay discounting task, which enriched the application of dual-system theory in development. Moreover, this study reveals the different internal mechanisms of cognitive system and reward system in adolescents and adults, which not only makes an in-depth discovery on the internal processing of the two systems, but also provides a new perspective and some theoretical support for promoting adolescents' delay discounting behavior in the future.