Facial expressions are central to human interaction, yet their role in strategic decision-making has received limited attention. We investigate how real-time facial communication influences cooperation in repeated social dilemmas. In a laboratory experiment, participants play a repeated Prisoner's Dilemma game under two conditions: in one, they observe their counterpart's facial expressions via gender-neutral avatars, and in the other no facial cues are available. Using state-of-the-art biometric technology to capture and display emotions in real-time, we find that facial communication significantly increases overall cooperation and, notably, promotes cooperation following defection. This restorative effect suggests that facial expressions help participants interpret defections less harshly, fostering forgiveness and the resumption of cooperation. While past actions remain the strongest predictor of behavior, our findings highlight the communicative power of facial expressions in shaping strategic outcomes. These results offer practical insights for designing emotionally responsive virtual agents and digital platforms that sustain cooperation in the absence of physical presence.

翻译：面部表情是人类互动的核心，但其在策略决策中的作用却鲜受关注。本研究探讨了实时面部交流如何影响重复社会困境中的合作行为。通过实验室实验，参与者分别在两种条件下进行重复囚徒困境博弈：一种是通过性别中立虚拟化身观察对手的面部表情，另一种则无法获取任何面部线索。利用最先进的生物识别技术实时捕捉并呈现情绪，我们发现面部交流显著提升了整体合作水平，并特别促进了背叛后的合作恢复。这种修复效应表明，面部表情有助于参与者以更宽容的方式解读背叛行为，从而促进宽恕并恢复合作。虽然过往行为仍是预测行为的最强指标，但我们的研究结果凸显了面部表情在塑造策略结果方面的沟通力量。这些发现为设计情感响应型虚拟代理和数字平台提供了实用见解，有助于在缺乏物理在场的情况下维持合作。