Medical Institute of Developmental Disabilities Research, Showa University, Setagaya-ku, Tokyo, Japan.
Department of Psychiatry, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan.
Hum Brain Mapp. 2020 Apr 15;41(6):1677-1688. doi: 10.1002/hbm.24903. Epub 2019 Dec 19.
Intergroup bias, which is the tendency to behave more positively toward an in-group member than toward an out-group member, is pervasive in real life. In particular, intergroup bias in trust decisions substantially influences multiple areas of life and thus better understanding of this tendency can provide significant insights into human social behavior. Although previous functional magnetic resonance imaging studies showed the involvement of the right temporoparietal junction (TPJ) in intergroup trust bias, a causal relationship between the two has rarely been explored. By combining repetitive transcranial magnetic stimulation and a newly developed trust game task, we investigated the causal role of the right TPJ in intergroup bias in trust decisions. In the trust game task, the counterpart's group membership (in-group or out-group) and reciprocity were manipulated. We applied either neuronavigated inhibitory continuous theta burst stimulation (cTBS) or sham stimulation over the right TPJ before performing the trust game task in healthy volunteers. After the sham stimulation, the participants' degrees of investments with in-group members were significantly higher than those with out-group members. However, after cTBS to the right TPJ, this difference was not observed. The current results extend previous findings by showing that the causal roles of the right TPJ can be observed in intergroup bias in trust decisions. Our findings add to our understanding of the mechanisms of human social behavior.
群体间偏见是指人们对群体内成员的行为比对群体外成员的行为更为积极的倾向，这种偏见在现实生活中普遍存在。特别是在信任决策中，群体间偏见会极大地影响人们生活的多个方面，因此更好地理解这种倾向可以为人类社会行为提供重要的见解。尽管先前的功能性磁共振成像研究表明右颞顶联合区（TPJ）参与了群体间信任偏见，但两者之间的因果关系很少被探索。通过结合重复经颅磁刺激和新开发的信任游戏任务，我们研究了右 TPJ 在信任决策中的群体间偏见中的因果作用。在信任游戏任务中，操纵了对手的群体归属（内群体或外群体）和互惠性。我们在健康志愿者中进行信任游戏任务之前，对右 TPJ 进行导航抑制性连续 theta 爆发刺激（cTBS）或假刺激。在假刺激后，参与者与内群体成员的投资程度明显高于与外群体成员的投资程度。然而，在右 TPJ 进行 cTBS 后，这种差异就不明显了。目前的结果通过显示右 TPJ 的因果作用可以在信任决策中的群体间偏见中观察到，扩展了先前的发现。我们的研究结果增加了对人类社会行为机制的理解。
