| 其他摘要 | Delayed gratification refers to the preference for larger later reward (LL reward) rather than smaller sooner reward (SS reward), and the ability of controlling himself when waiting for the LL reward. It's not only the core of the self-control mechanism, but also an important part in one's socialization and emotional regulation. In laboratory, researchers often use delay discounting task to measure delayed gratification ability which is weighed by discounting level. It's found that people tend to choose the SS reward compared to LL reward. And when entering into adolescence, teenagers' preference to LL reward would be strengthened一teenagers discount less and have stronger ability of delaying gratification in growing process. However, according to the Dual System Model of Puberty, the socioemotional system relevant to sensation seeking develops rapidly during early adolescence, and the cognitive control system responsible for inhibiting impulses develops more slowly. The different maturation time makes one hardly restrain himself from risky and reckless behavior, which is inconsistent with the developmental trajectories of delayed gratification. The reason is worth exploring.
We utilize the behavioral and structural imaging data of Chinese Color Nest Project to investigate delayed gratification. This project recruit children and teenagers aging from 6 to 18 years old through an accelerated longitudinal design, and has conducted a baseline test and two tracking tests, with an interval of 21.6 months and 18.2 months, respectively. In each participation, subjects would finish the delay discounting task, scan T1 and T2 in functional magnetic resonance imaging to collect brain morphological data including cortical surface area and sub-cortical segmented volume. Overall, 155 participants are included in the cross一sectional study (10.29士2.42 years), while there are 54 participants enrolled into at least two tests, 130 measurements totally. In data analysis, we firstly use hierarchical multiple regression analysis and Likelihood Ratio Test to verify the two systems' effects on delayed discounting behavior. Then, we would establish a structural equation model with the systems as the predictors and delay discounting as the dependent variable. By comparing the standardized value of the two systems on delay discounting behavior, we could find whether the cognitive control system has a larger effect on delayed discounting behavior than the socioemotional system does.
Results indicate that, in both cross-sectional study and longitudinal study，performance in delay discounting task increased with age during the transition into adolescence. Hierarchical regression analysis and Likelihood ratio test show that cortical surface area of cognitive control brain system (such as inferior parietal, ventrolateral PFC) and socioemotional brain system (such as cingulate cortex, orbitofrontal cortex) could explain the extra variance of delay discounting behavior. The subcortical segmented volume (including putamen and nucleus accumbens) also influenced delayed discounting in the longitudinal study .Structural equation model analysis reveals that, in cross-sectional study, the standardized value of effect from cognitive control system on delay discounting performance would increase as individual develops into adolescence, and surpass that of the socioemotional system. In longitudinal study, the socioemotional changes faster between two tests, but the standardized value of effect on delayed discounting performance is smaller than that of the cognitive control system.
In conclusion, although the socioemotional system develops faster in the transition into adolescence, it exerts a smaller effect on delayed gratification than the cognitive control system does. And the influence of cognitive control system would be strengthened as age increases. This research can expand our understanding of neural mechanism of delayed gratification in childhood and adolescence. It also verifies and develops the dual-system model and delayed discounting model. Besides, when children and adolescents with weaker delayed gratification receive clinical treats, our outcome could provide reference for targeted therapies. |
修改评论