Social situations may vary in the severity of conflict between self-interest and collective welfare, and thereby pose collective action problems that might require different institutional solutions. The present study examines the effect of conflict of interests on beliefs, norms, cooperation, and choice of sanctioning institutions in social dilemmas across two experiments (total N = 1304). In each experiment, participants interacted in a public goods game (PGG), and a modified PGG with institutional choice using a 2 (conflict of interests: low vs. high) × 3 (institutional choice: peer punishment/no sanction vs. centralized punishment/no sanction vs. gossip plus ostracism/no sanction) between-participants design. More severe conflict of interests reduces individuals' own cooperation, first-order beliefs about others' cooperation, second-order normative expectations and personal norms of cooperation. This pattern is pronounced over time in repeated interactions. We did not find that conflict of interests influenced the choice to establish a sanctioning institution. Taken together, the challenges arising from stronger conflicting interests can cause the collapse of cooperation, hinder the emergence of trust and norms of cooperation, but do not provide the impetus to support a sanctioning institution to promote cooperation. Implications for solving public goods dilemmas that contain a severe conflict of interests are discussed.

社会情况可能因自身利益与集体福利之间冲突的严重程度而异，从而引发可能需要不同制度解决方案的集体行动问题。本研究通过两项实验（总计N  = 1304）考察了利益冲突对社会困境中的信仰、规范、合作和制裁机构选择的影响。在每个实验中，参与者在公共物品博弈（PGG）中进行互动，并在修改后的 PGG 中进行制度选择，使用 2（利益冲突：低与高）× 3（制度选择：同伴惩罚/不制裁与集中惩罚） /无制裁与八卦加上排斥/无制裁）参与者之间的设计。更严重的利益冲突会降低个人自身的合作、对他人合作的一阶信念、二阶规范期望和个人合作规范。随着时间的推移，这种模式在重复的互动中变得明显。我们没有发现利益冲突影响了设立制裁机构的选择。综合来看，更强烈的利益冲突带来的挑战可能会导致合作崩溃，阻碍信任和合作规范的出现，但不会为支持制裁机构促进合作提供动力。讨论了解决包含严重利益冲突的公共产品困境的影响。