自我损耗促进冲动决策：来自行为和ERPs的证据

该研究以自我控制资源模型为理论框架, 采用行为实验和ERPs技术考察自我损耗对冲动决策的影响。实验1采用Stroop任务操纵自我控制资源并采用延迟折扣任务考察被试的决策冲动性, 实验2采用同样的实验任务并同时采用ERPs技术记录高、低自我损耗者在随后决策任务中的脑电成分。行为结果发现, 在控制心境、特质自我控制水平以及风险偏好等无关变量后, 高损耗者比低损耗者在延迟折扣任务上的折扣程度更大。ERPs结果发现, 不论延迟金额大小, 高损耗者在左侧额区诱发的N1波幅显著小于低损耗者; 高损耗者在右半球诱发的P2波幅显著大于低损耗者。研究表明, 自我损耗抑制决策早期左侧额区的激活水平, 个体因而无法识别冲突以及抵制即时满足的诱惑, 这促使他们采用直觉启发式进行决策, 最终导致冲动决策的产生。

Ego Depletion Promotes Impulsive Decision: Evidences from Behavioral and ERPs Studies

The role of self-control in the process of decision-making has become a hot issue recently. Impulsive decision often brings a variety of undesired consequences and therefore reducing such kind of decision is conducive to preventing unexpected accidents that may occur in daily life. To the best of our knowledge, little work has been done to investigate the effect of self-control on impulsive decision-making. To fill in this gap, the current study aims at exploring how self-control influences impulsive decision-making using behavioral and electrophysiological experiments. According to the self-strength model of self-control, a prior exertion of self-control resources may consume the limited resources of self-control (i.e., ego depletion), which in turn undermines subsequent self-control performance. In addition, based on the prefrontal-subcortical balance model of self-regulation, higher or lower activation of prefrontal cortex is one of the important neural mechanisms that results in self-control failure. In light of these, the present study hypothesizes that ego depletion may increase impulsive decision-making (experiment 1 and 2), and this effect may be indicated by lower amplitude of N1 and higher amplitude of P2 (experiment 2). Self-control resources depletion was manipulated by Stroop task, a task that had been consistently proved to be effectively distinguish high and low self-control resources in previous researches. In the current study, participants assigned to high depletion condition completed 160 trails, which consisted of 140 incongruent trials and 20 neutral trails, whereby those in low depletion condition finished 140 congruent and 20 neutral trials. Impulsive decision-making was assessed by delay discounting task, a task that had frequently been employed to examine participants’ impulsivity in decision-making. A number of confounding variables were specified and controlled (i.e., mood, trait self-control, and risk-preference). In experiment 1, participants (N = 50) were randomly assigned to either low or high depletion condition. After completing the Stroop task followed by manipulation checks, they worked on the delayed discounting task. The procedure of experiment 2 was very similar to the one of experiment 1 except that participants’ EEGs were recorded by 32-channel ERPs equipment while they were carrying out the delaydiscounting task (N =32). The results showed that after ruling out the intervening variables, participants in high depletion condition showed more discounting in the delay discounting task than those in low depletion condition (experiment 1 & 2). Moreover, while participants with their self-control resources highly depleted were working on the delayed discounting task, the N1 of left prefrontal cortex displayed lower amplitude whereby the P2 of right hemisphere showed higher amplitude in comparison of those whose self-control resources were relatively intact (experiment 2). In sum, these findings suggest that activation of left prefrontal cortex is inhibited by ego depletion in the early period of decision-making process, and thus people are less likely to detect conflicts between choices and override the temptation of immediate reward. This leads the experiential system to dominate the process of decision-making, and it, in turn, results in impulsive decision. The current study demonstrates the importance of self-control in the process of impulsive decision-making and provides insights into prevention for this problem.