Abstract: For several decades, psychologists and neuroscientists have investigated ethical dilemmas to deeper understand the cognitive and brain mechanisms. Thus, typical dilemmas such as trolley dilemma and the footbridge dilemma have served as innovational experimental materials. Based on previous studies，the present study used event-related potential to investigate how the protagonist in moral dilemmas influenced our moral decision-making or how kinship influences moral dilemma decisions and to reveal the cognitive and neural mechanisms of dilemma decision-making relative to different blood kinship. We specifically adapted 10 revised versions of typical moral dilemma scenarios mainly developed by ethicist Greene (2003) and expanded it to reflect harm, care, and altruism. According to blood relationship, we took kinship’s name (the task types) as protagonists in the dilemma situation to investigate how kinship influenced moral judgment (Father’s name as lineal kin, Uncle’s name as close relative and the Acquaintance’s name as baseline). After the participants read the scenario description (no time limit), the kinship’ names was present and the participants were asked to decide whether or not to rescue the kinship as quickly as possible. We hypothesized that it would be much easier for subjects to decide rescuing Father, compared to Uncle and Acquaintance, and this should be reflected in an ERP activation pattern. Specifically, it would be related to an early relative positivity (P2) and a late positive component (LPC) in three (Father, Uncle and Acquaintance) conditions. In the experiment，we found that there was a main effect of task types (2 relatives and a Acquaintance) for reaction time. The time of choosing to rescue Father is significantly faster than that of choosing to rescue Uncle and Acquaintance. The rate for task types is also significantly different. The rate of choosing to rescue Father is higher than Uncle and Acquaintance. In addition, a repeated ANOVA measure on N1 amplitudes and latencies demonstrated no significant effects, but Father elicited a much more positive deflection (P2 average amplitude) than did Uncle and Acquaintance. More importantly, Father elicited a much more positive deflection (LPC average amplitude) than did Uncle and acquaintance. The results showed that three types of names were approximately equal in size, word length and complexity. It also indicated that we were presumably sensitive to the suffering and the needs of lineal relative compared with other relative or acquaintance. In addition, observing from the grand averaged waveforms and topographical map, we inferred that the right central and right parietal sites could be involved in kinship bias processing in moral dilemma and the P2 and LPC might be involved in the dilemma interference resolution and execution of willed actions. Compared with kinship bias effects or self-referential effect that has been demonstrated in previous studies，the present study used electrophysiological methods to verify the existence of kinship bias effect that harm directed towards Father had a stronger impact than harm directed towards other kin or acquaintance. It further confirmed that lineal relative stimuli (e.g. Father) were processed well compared to close relative stimuli (e.g. Uncle) and acquaintance stimuli. The results showed that lineal relative was closer and more important to the well-known individual self compared with other stimuli. Father could be detected and processed preferentially compared with other kin and acquaintance who are far from one’s self. In addition, Subjects would be conscious of conflict discovery and conflict resolution processes in P2 and LPC phase. The P2 and LPC component might be related to dilemma interference resolution processes and modulate or control cognitive conflict when making dilemma decisions with regard to lineal relative, close relatives and acquaintance. These results may indicate that kinship bias effect was present but only vaguely．

Key words: Moral dilemma decision-making, Kinship bias, ERPs, P2, LPC

摘要： 采用事件相关电位技术，考察个体在道德两难情境下对不同亲属的加工特征及其亲属偏见效应。道德两难情境中的主人公为被试的两个亲属（父亲、叔父）和一个熟人，要求被试阅读道德两难情境故事后，对是否愿意救助故事中主人公作出判断。结果发现，直系亲属（父亲）比旁系亲属（叔父）和熟人诱发了更大的P2和LPC平均波幅，而旁系亲属与熟人之间并无显著差异。研究表明了个体对直系亲属更为关注和敏感，表现出明显的亲属偏见效应。

关键词: 道德两难判断, 亲属偏见, ERP, P2, LPC