Displaying partial trust in exchanges between strangers is a common practice, but it does not effectively promote reciprocation. This is an intriguing phenomenon that warrants investigations regarding social mechanisms that can promote reciprocation without changing the level of trust. We seek to examine, given a partial-trust act, whether framing the motive underlying the act as prosocial (mutually beneficial) can promote reciprocation in an exchange between strangers. Across three experiments in the United States, we found that trustor prosocial (vs. no-motive) framing can promote trustee reciprocation through trustee felt obligation and that this effect is particularly strong among trustees with a strong rather than weak exchange orientation. Concurrently, this prosocial framing effect can operate serially through trustee perceived invitation for exchange and felt obligation. Our findings help address the conundrum of promoting reciprocation without introducing deleterious uncertainty about social motives given a partial-trust act that is prevalent in exchanges at zero acquaintance.

在陌生人之间的交流中表现出部分信任是一种常见的做法，但并不能有效地促进互惠。这是一个有趣的现象，值得对可以促进互惠而不改变信任水平的社会机制进行调查。我们试图检查，给定部分信任行为，将行为背后的动机定为亲社会（互惠互利）是否可以促进陌生人之间交流中的互惠。在美国的三个实验中，我们发现信任人亲社会（与无动机）框架可以通过受托人感到的义务促进受托人互惠，并且这种效果在具有强而不是弱交换导向的受托人中尤为明显。同时，这种亲社会框架效应可以通过受托人感知到的交流邀请和感受到的义务来连续运行。鉴于在零熟人的交流中普遍存在的部分信任行为，我们的研究结果有助于解决促进互惠而不引入有害的社会动机不确定性的难题。