Transcranial Direct Current Stimulation Modulates The Effects Of Black And White Color On Moral Judgment

In recent years,the events of moral deficiency have highlighted the importance and urgency of moral cultivation.In addition to traditional ways of moral education,emerging non-invasive neural regulation techniques can change people’s behavior by stimulating specific brain regions,which may be a new type of intervention for moral enhancement.Transcranial direct current stimulation(tDCS)is a safe and portable non-invasive neural regulation technique,which has been well used in regulating individuals’ social cognition and behavior.This study intends to use this technique to intervene in the moral processing of healthy individuals.The researches of moral embodiment show that specific physical perception could have a significant effect on abstract moral processing.It has been found that the visual perception change of black and white color can affect the moral judgment of individuals,that is,there exists the moral black and white metaphor of "black is bad,while white is good".But color metaphor sometimes can induce negative effects such as misjudgments by referees.According to the dual processing model of moral judgment,the dorsolateral prefrontal lobe(DLPFC)is an important brain area related to cognitive control processing.One of the main goals of this study is to regulate the excitability of DLPFC to explore the key role of this brain region in moral black and white metaphor.Furthermore,most of the current cognitive neuroscience research focuses on the influence of emotion as an irrational factor on moral judgment,but neglects another important potential irrational factor——the influence of perception on moral judgment.It is unclear that how specific physical perception affects abstract moral processing.Therefore,another goal of this study is to examine the important role of the occipital cortex(OC)associated with visual perception processing in moral black and white metaphor.This study consists of two experiments.The first experiment used tDCS to regulate the DLPFC to explore the influence of the cortical excitability changes in DLPFC on moral black and white metaphor.In the second experiment,tDCS was used to regulate the activation of OC to investigate the key role of OC in moral black and white metaphor processing.The results showed that:(1)There was a significant interaction between color and moral types in both experiments.Under the immoral condition,the reaction time(RT time)of white words was significantly longer than that of black words.But under the moral condition,the RT time of black words was significantly longer than that of white ones.The results showed that black and white color had a significant impact on moral judgment;(2)Compared with sham condition,cathode stimulation over DLPFC induced larger moral Stroop effect between black and white,and anode stimulation reduced the moral Stroop effect between black and white.These results showed that decreasing the excitability of the DLPFC could enhance the influence of black and white on moral judgment,while increasing its excitability could reduce the influence of black and white on moral judgment.(3)Compared with the sham stimulation,anode stimulation over OC induced larger moral Stroop effect.And there was no significant difference between the white and black words under the cathode stimulation condition.It showed that improving the excitability of the OC would enhance the influence of black and white on morality,and vice versa.Above all,the results of this study indicated that using tDCS to regulate the excitability of DLPFC and OC could regulate the processing of moral black and white metaphor.Increasing DLPFC or inhibiting OC activation could weaken the influences of black and white color on moral judgment.Conversely,inhibiting DLPFC or increasing OC activation could enhance the effects of black and white on moral judgment.From the perspective of body morality and transcranial direct current stimulation,this study investigated the effect of excitability changes of the DLPFC and the OC on moral black-and-white metaphor.The causal relationship between these two brain regions and moral black-and-white metaphors is a good complement to the study of traditional moral metaphors.At the same time,this study uses tDCS technology to carry on two-way non-invasive intervention and regulation to abstract moral judgment processing,which provides ideas and basis for the use of non-invasive neural regulation technology in moral cultivation in the future.