Abstract:

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.

Key words: ego-depletion, self control, impulsive decision, delay discounting task, event-related potentials