中文摘要：

使用董事会成员的性别、年龄、学历和任期四个个人特征构建群体过度自信的衡量指标，实证检验董事会过度自信对我国上市公司过度投资的影响，并分析公司治理机制对影响的调节效应。研究结果表明，董事会决策时容易产生群体过度自信，且该过度自信对公司过度投资具有显著的正向作用。从公司治理因素角度，股权集中度对董事会过度自信与过度投资之间的关系具有正向调节作用，即股权集中度越高，董事会越可能存在话语权强大的董事，这会增加董事会决策的极化倾向，进而增加过度自信导致的过度投资。董事会规模和独立董事抑制董事会过度自信引发的过度投资的效果不明显。

英文摘要：

According to the theory of group decision and groupthink, we empirically test the influence of overconfidence of board on the overinvestment of Chinese listed companies based on the board group overconfidence variable which is constructed by gender, age, education and tenure of board members. Furthermore, we study the moderating effect of corporate governance on the influence. The results indicate that the board group decision leads to group overconfidence easily. Based on the factors of corporate governance, board group decision has no effect on reducing the overconfidence of individual. There is significant positive correlation between board group overconfidence and corporate overinvestment. We also find that the higher ownership concentration, the more possible to be director who has strong discourse power. This will increase the possibility of board group polarization, and increase the level of corporate overinvestment. Increasing board size and independent directors have no use to decrease the overinvestment which is initiated by board group overconfidence.