道德判断影响大脑对公平行为的早期评价

Moral judgment modulates fairness consideration in the early outcome evaluation stage

近年研究发现,社会距离、社会排斥、社会评价等社会因素与公平行为共同调节了早期结果评价过程,但目前研究尚未探讨社会因素中道德判断对公平决策的影响及其神经机制.本研究在道德句子启动下与最后通牒范式结合并记录脑电数据,探究道德判断(3水平:杀人犯、献血者、普通人)与提议公平性(2水平:公平、不公平)对响应者的决策行为影响.行为结果发现,献血者不公平提议的接受率显著高于杀人犯,杀人犯公平提议的接受率显著低于献血者与普通人.脑电结果发现,道德判断和提议公平性共同调节了个体的FRN(feedback-related negativity)波幅,仅发现献血者条件下不公平提议比公平提议诱发更负的FRN波幅.在P300成分上发现公平比不公平提议诱发了更大的波幅,且不受道德判断的影响.本研究结果表明,道德判断与公平准则冲突时,个体更依赖于道德判断进行决策.个体对高道德水平者存在更高的公平期待,对其不公平行为诱发了更强的负性情绪.FRN反映了违反社会准则的不公平行为,这一结果早期评价过程也受到了道德判断等社会因素的调节作用,但P300反映的晚期评价过程则不受道德判断的影响.

Morality,concern for the welfare of others,is an important criterion of how individuals treat others,including justice,fairness,and rights.Moral judgment is the process of evaluating the behavior of others and oneself according to social norms.Morality might affect social cooperation with others by entailing the belief that someone should be rewarded or punished.The ultimatum game is a classic paradigm that can be used to study the fairness behavior of social cooperation.Previous studies have shown that some social factors(e.g.,social distance,social exclusion,and social evaluation)influence fairness behavior in the ultimatum game.Using the event-related potential(ERP)technique to examine the neural basis of the ultimatum game,studies found that feedback-related negativity(FRN)was modulated by social factors.This effect indicates that the influence of social factors mainly appears in the early stage of outcome evaluation.However,the influence of moral judgment on social cooperation and its neural mechanism remains unclear.The present study focused on whether moral judgment would affect fairness consideration in the early outcome evaluation stage.For this purpose,we used moral sentences within the ultimatum game to assess the influence of moral judgment and fairness of offers on decision-making.A total of 25 participants who acted as respondents completed the ultimatum game with blood donors,murderers,and unidentified individuals as proposers.A moral sentence(e.g.,He is a blood donor)was given as a reminder of the moral identity of the players before each round.Participants were told that other players would gain$50,and proposers would make an allocation offer.There were five types of allocation offers:$5,$10,$15,$20 or$25.Participants were asked to accept or reject the offers.At the same time,the ERP was locked to the onset of the offers.The acceptance rate of each offer was included in the behavioral data.The dependent variable was the acceptance rate of the five allocation offers and moral primes were the independent variable when performing one-way ANOVAs.Regarding ERP data,$5 and$10 were considered as unfair offers and$20 and$25 as fair offers in order to analyze the amplitudes of FRN and P300.Two-way repeated measures ANOVAs(moral judgment,three levels;offer fairness,two levels)were performed to compare ERP data.Behavioral results showed that the acceptance rate of unfair offers from blood donors was significantly higher than that of murderers.Furthermore,the acceptance rate of fair offers from murderers was significantly lower than that of blood donors and unidentified individuals.ERP results revealed that the FRN amplitude was more negative-going in response to unfair than to fair offers.The fairness of offers modulated FRN amplitude only regarding blood donors,but not for murderers and unidentified individual conditions.P300 was larger for fair offers compared to unfair offers and was not affected by moral judgment.These results indicate that when moral judgment conflicts with the fairness criterion,individuals might rely on moral judgment to make decisions.People may have a higher expectation of fairness from individuals with high moral standards,while unfair behaviors could induce strong negative emotions.FRN represents unfair behaviors that violate social norms and shows that the early outcome evaluation stage is also modulated by moral judgment,while the late stage is independent of moral judgment.