Social capital theorists posit that association members are key agents for propagating norms of trust and trustworthiness from within associations toward the society as a whole. Nevertheless, others claim that social capital is primarily bonding, that is, it helps ingroup members better achieve internal goals, but little benefits or even costs carry over to the rest of society. We deploy experimental methods to probe into whether social capital in associations has a predominantly bridging or bonding nature. We compare members’ behavior in anonymous Trust Games with behavior by a demographically comparable sample of non-members. We find that (a) Members are significantly more trusting and trustworthy than the general population both when interacting with fellow members and with people from the general population; (b) Members trust and repay trust from people from the general public nearly at the same level as they do with fellow members. Therefore, most of social capital existing within associations “bridges” over to the rest of society. We quantify 83% of additional trust, and 71% of additional trustworthiness existing in associations vis-à-vis society at large to be bridging and the remainder to be bonding. (c) Association members are no more optimistic or less accurate in predicting others’ behavior than people from the general public. (d) Increased involvement in association activities is not correlated with increased pro-sociality.

社会资本理论家认为，协会成员是从协会内部向整个社会传播信任和可信规范的关键代理人。然而，其他人则声称社会资本主要是纽带性的，也就是说，它可以帮助群体内的成员更好地实现内部目标，但很少有好处甚至成本可以转移到社会其他人身上。我们采用实验方法来探讨协会中的社会资本是否具有主要的桥接或粘合性质。我们将匿名信任游戏中的会员行为与人口统计上可比较的非会员样本的行为进行比较。我们发现 (a) 在与其他成员以及与一般民众互动时，成员明显比一般民众更加信任和值得信赖； (b) 会员对公众的信任和回报与对其他会员的信任程度几乎相同。因此，协会内存在的大部分社会资本都“桥接”到社会的其他部分。我们量化了协会与整个社会之间存在的 83% 的额外信任和 71% 的额外可信度，作为桥梁，其余的作为纽带。 (c) 协会成员在预测他人行为方面并不比普通公众更乐观或更不准确。 (d) 增加参与协会活动与增加亲社会性无关。