The Cognitive And Neural Mechanism Of Acceptance/Rejection Decision-Making In Economic Decision-making

Acceptance/rejection decision-making is that individuals faced with two completely different quality alternative program (acceptance/rejection), they have to make a decision based on their subjective assessment. This kind of decisions are ubiquitous in daily life, but there are few laboratory studies on the decision-making process. Rational economic decision theory considers people as completely rational "economic man", they make their decisions always based on the pursuit of the maximum expected value, regardless of other factors.In fact, it is not the case in most realistic decision-making situations, such as the same individual in different contexts, as well as decisions made by different individuals in the same context, the decisions may be influenced by the personal status of the decision-makers and the conditions. However, the existing decision-making theories have difficulty in explaining the psychological mechanisms of this kind of decision-making process. Thus, the further study of this kind of decision-making is not only of great scientific value, but also has significant practical meaning. Little is known about the cognitive and neural mechanisms underlying "acceptance/rejection" Decision-making, despite some behavioral and neural studies have been done. Therefore, adopting the Gamble Task which changes both probability and value, the present study is aimed to investigating the cognitive mechanism of the "acceptance/rejection" Decision-making under three conditions---- expected value is more than the referenced value, expected value is less than the referenced value and expected value equals to the referenced value (ExperimentⅠ); The second experiment, which was based on the first experiment, used the fMRI to explore the neural mechanism of the "acceptance/rejection" Decision-making under the condition that expected value less than the referenced valve(ExperimentⅡ). By manipulating probability and value, there are three gambling decision-making conditions(exp. a: expected value is greater than the referenced value, exp. b: expected value is less than the referenced value, exp. c:expected value equals to the referenced value) in ExperimentⅠ, in which subjects have to make their decisions:to bet, then they will get their rewards by real probabiity, or not to bet, then they will get a certain reward of 3. The results showed that:(1) when the expected value is greater than the reference value, individuals will choose to accept all gambles in theory (ie, the acceptance rate of 100%), but the actual acceptance rate is only 83%; when the expected value is less than the reference value, individuals will choose to give up gambles in theory (ie, acceptance rate of 0), but the actual acceptance rate of up to 34%; when the expected value equal to the reference value, the probability of individuals choosing to accept or reject gambles should be the same in theory (ie,50%), but the actual acceptance rate is 53%. This demonstrats that the choices of subjects are contrary to rational economics decision-making theory. (2) The rates of acceptance increased with probability, and there was a significant positive correlation between them(exp. a:r=0.952, p=.000; exp.b:r=0.968, p=.000; exp. c: r=0.948, p=.000); however, the conditon of value was contrary to the probability, there was a weak negative corrlation between the rate of acceptance and value(exp. a:r=-0.769, p=.000; exp.b:r=-0.761, p=.000; exp. c:r=-0.803, p=.0O0). (3) when expected value is more than the referenced value, probality and probability*value (expected value) entered into the regression equation successively, the predicting rate of model is 84.7%; while in the "less" condition, probability*value(expected value), probability and value entered into the regression equation successively, the predicting rate of model is 77.9%; however, in the condition of "equal", there was only probability, the predicting rate of model is 64.7%. This shows that when the expectated value is greater than or equal to the reference value, probability has greater weight in decision-making process; when the expected value is less than the reference value, the expected value has greater weight in the subjects’ decision-making process.ExperimentⅡwas aimed to exploring the neural mechanism of "acceptance/rejection" Decision-making in the situation of "LESS". The behavioral results have showed that:(1) The rate of acceptance is 33%,which is much more than the theoretic acceptance(0%). (2) The rate of acceptance rase with the increasing of probability (r=0.948, p=.000) and the decreasing of value(r=0.274, p=.286). (3) Probability*value(expected value) and value entered into the regression equation successively, the predicting rate of model is 77.1%.The fMRI results showed that:(1) The cerebral regions sensitive to the choice process (the "accept" decision minus the "reject" decision) mainly included right inferior frontal gyrus(BA9), left/right insula(BA13), left/right lingual gyrus(BA18), right precuneus(BA7), right thalamus, right middle frontal gyrus(BA6), left lentiform nucleus, left superior parietal(BA7), left inferior temporal gyrus(BA37), right superior temporal gyrus(BA38), left/right cuneus(BA18), left posterior cigulate(BA31), left anterior cingulate(BA32) and so on. There is a marginal negative linear correlation between the right insula(BA13) and the behavioral results of the rate of acceptance (r=-0.468, p=0.058). (2) The cerebral regions sensitive to the probability (including three levies----high/middle/low) mainly included left/right superior parietal(BA7), right middle frontal gyrus(dmPFC, BA13), left/right lentiform nucleus, right cingulate gyrus(BA32), left cingulate gyrus(BA23), left precuneus(BA7), left anterior cingulate gyrus(BA32) and so on. There is a significant positive linear correlation between the right superior parietal lobule(BA7) and the behavioral results of the rate of acceptance (r=0.438, p=0.001), while a significant negative linear correlaton for left ACC(r=-0.447, p=0.001). (3) The cerebral regions sensitive to the value(including three levies----high/middle/low) mainly included left/right superior parietal(BA7), right middle frontal gyrus(dmPFC, BA13), left/right lentiform nucleus, right cingulate gyrus(BA32), left cingulate gyrus(BA23), left precuneus(BA7), left anterior cingulate gyrus(BA32) and so on. There is a significant negative linear correlation between the PCC(BA23) and the behavioral results of the rate of acceptance (r=-0.413, p=0.003).Based on the present study results which included ExperimentⅠand ExperimentⅡ, we can conclude that:(1) During the whole process of Acceptance/rejection Decision-making, individuals’ decision violates the theory of economic decision-making, they have different standards in different conditions: when the expected value is greater than or equal to the reference value, probability has greater impact on the decision-making process, while individuals are more inclined to make decisions taking into account the probability and potency when the expected value is less than the referenced valur. (2) Acceptance/ rejection Decision-making process has activated many brain regions. However, The cerebral activation data on right superior parietal lobule (BA7) and left ACC fit well with the behavioral data in probability condition, indicating the important regions involved in the probability processing of decision-making; meanwhile, left PCC involved in the value processing of decision-making; simultaneously, the negative emotion resulted from right insula(BA13) may regulate the "rejection" decision-making during the whole process.