Abstract: When one receives information from group that inconsistent with his own decision, he may shift his decision and conform to the majority, we call this phenomenon Informational Conformity. From now, the mechanism underlying this phenomenon is still inconclusive. However, when take another look at it, Informational Conformity is also a phenomenon of decision-shifting. And according to the Two-Stage Dynamic Signal Detection (2DSD), the decision confidence may have a specific role in decision-shifting. Decision confidence reflects one's belief in the optimality or correctness of his decision, and humans often use it to adjust their decisions. 2DSD supposes that a judge does not simply shut down the information accumulation process after making a choice but continues to accumulate information to make a confidence rating. So the confidence rating is a function of the information collected at the time of the choice plus the information collected after making a choice. Thus, one's confidence rating will increase if the information collected after making a choice support his choice, and decrease if the information conflict with his choice, then their decision may be changed. Hence, this study hypothesizes that the decision confidence may have an important effect on Informational Conformity. With a modification of the JAS (judge-advice-system) paradigm, we explored the role of decision confidence in Informational Conformity. 30participants (12male), age 19-25 were recruited from undergraduate. We made 80 rectangular pictures (11.43cm*15.24cm) by CAD drawing software, and divided it into two irregular parts with a curve. Participants were asked to pick out the larger one, and rated their confidence on a scale from 1 (very uncertain) to 6 (certain) of their decision. After rating, we provided participants with the information of others’ decisions on that very picture for reference. Then they estimated their confidence rating again or shift their choice to another. At the end of the experiment, participants were given a test of Cognitive Style. The results showed that the Cognitive Style score was not correlated with the quantity of confidence ratings changed or the probability of decision shifting, implicating individuals with different cognitive styles has no difference in information taking. And we found that: (1) participants shifted their decisions and conform to the majority merely in against condition; (2) the group information had a significant influence on individual's decision confidence. When the information one received supported for his judgment, his confidence rating increased, and when the information against his judgment, his confidence decreased. What's more, compared to support information, against information caused greater changes in confidence, which suggesting a negative effect in information taking;(3) in against condition, and the degree of decline in confidence could positively predict the probability of decision-shifting. In conclusion, the findings revealed that the decision confidence played a key role in Informational Conformity.When individual receives opposing information of his initial decision from group, his decision confidence ought to be decreased, and this leads to his decision shifting, showing a conformity behavior. The findings enrich the decision theory, in addition, it also suggests that any factor could affect confidence may have an effect on one's decision, and reminds us that we should use information rationally when making decision

Key words: group information, decision confidence, decision-shifting, Informational Conformity

摘要： 研究采用JAS范式，通过操纵群体信息的性质（支持和反对）以及一致性程度，考察了决策信心在信息化从众过程中的作用。结果表明：（1）个体仅在接收到反对信息时会发生决策的偏转，表现出从众；（2）群体参照信息能够显著影响个体的信心：支持性的群体信息使个体的信心显著增高，而反对性的群体信息使信心显著降低，且表现出一种“负性偏向”（即个体对来自群体的负性信息更加敏感）；（3）在反对条件下，个体信心降低的程度能够很好地预测其决策偏转的概率，即信息化从众行为。这说明，决策信心可能在信息化从众中起着核心的中介作用——反对性的群体信息使得决策信心下降，而决策信心的下降导致了决策的偏转，从而表现出从众行为。

关键词: 信息化从众, 决策信心, 群体信息, 决策偏转