The Cognitive And Neural Mechanism Of The State And Strait Delay Discounting

Intertemporal choice is that decision makers frequently balance the costs and benefits of decision making processes which occur at different times. As Adam Smith first recognized, such decisions not only affected one’s health, wealth, and happiness, but might also determine the economic prosperity of nations. In intertemporal choice, an important discovery is the delay discounting phenomenon which refers to that compared the current or recent benefits or loss, people always tend to give the future benefit or loss smaller weight. At present, the researchers have had a lot of researches of phenomenology, cognition and calculation, and the neural basis in intertemporal choice field. In the Trends in cognition science, Peters et al.(2011) thought that we should exploit the delay discounting phenomenon from the status factors and the strait factors angles. Thus, the present research exams the cognitive and neural mechanism of intertemporal choice from the status factor (the poverty-affluence status) and the strait factor (the self-control ability) angles of decision-maker.Study I exams the cognitive mechanism of intertemporal choice affected by the poverty-affluence status, using the explicit priming (Experiment A), the implicit priming (Experiment B) of the poverty-affluence cues, and the manipulation of temporary perceptions of poverty and affluence status (Experiment C). In study I, the results showed:(1) In our first two experiments (Experiment A and Experiment B), participants primed with the poverty pictures preferred more immediate gratification in the posttest task than in the pretest task, and the result is significant. Compared with the pretest task, participants primed with the affluence pictures tended to delayed gratification in the posttest task, but it was not significant.(2) By the manipulation of the actual poverty and affluence status (Experiment C), individuals in the poverty state chose more smaller and immediate rewards than individuals in the affluence state. Through the PANAS, we found that overall mood state was not affected by our manipulations. In general, the results of study I suggested that the poverty state affected the delay discounting rate, and induced individuals to choose the immediate rewards. Study Ⅱ exams the neural basis of self-control in intertemporal choice by a novel "free-choose and followed choose" task and the fMRI measures. The intertemporal choice task offered two types of choices:forced-choice asking subjects to follow the computer’s choices and free-choice indicating subjects to decide for himself/herself. By the contrast of the different selecting methods, it can distinguish the two stages of intertemporal choice:the valuation stage and the choice stage, which then separated the valuation process and the self-control process. In study Ⅱ, the results showed: During intertemporal choice, the neurobiological mechanism could include two process stages:a valuation stage and a choice stage. The contribution of subjective valuation may be recruited during the valuation stage, and self-control process may be recruited during the choice stage. Ventral striatum (VStr), ventralmedial prefrontal cortical (vmPFC), and posterior cingulate cortical (PCC) activation were correlated strongly with the subjective valuation in the valuation stage, whereas dorsolateral prefrontal cortical (DLPFC), and inferior frontal gyrus (IFG) were correlated with self-control processes in the choice stage. Furthermore, that the activity of these areas in the left DLPFC and right IFG were negatively correlated with discounting rates, such that more impulsive subjects showed less neural activation in these regionsBased on the present study results which included Experiment Ⅰ and Experiment Ⅱ, we can conclude that:(1) Poverty cues can change the individuals’ delay discounting rate and lead to short-term choices. The reason may be that the poor may feel that their poverty state in society prevents them from accessing to the same opportunities as the rich and that the choosing of immediate rewards, in part, derives from a desire to correct for the poverty state.(2) The single-and dual-valuation accounts agree that the choice of an option results directly from the comparison of their valuations without additional intervening process such as self-control. The results of study Ⅱ suggested that there are two process stages in intertemporal choice:the subjective valuation stage and choice stage. The valuation network can be activated in the valuation stage, and the self-control network can be activated in the choice stage. Furthermore, the results showed self-control may play a important role in intertemporal choice, potentially reconciling different neural accounts of the intertemporal choice.Future research will exploit the cognitive and neural mechanism of intertemporal choice from the status factors and the strait factors angles. Firstly, the status factors may affect the intertemporal choice, such as, economic conditions, emotional states, and physiological demand. Future research will exam the cognitive and neural mechanism of how the status factors affecting the intertemporal choice using the behavioral research and the cognitive and neural technology. Secondly, the strait factors include the valuation ability, impulsive and self-control ability, time perception ability, and prospection ability. Future research will exam the neural mechanism of how the strait factors affecting the intertemporal choice.