Emotional expressiveness in robots has attracted increased research interest, and development of this technology has progressed in recent years. A wide variety of methods employing facial expressions, speech, body movements, and colors indicating emotional expression have been proposed. Although previous studies explored how emotional expressions are recognized and affect human behavior, cooperative and competitive human-robot relationships have not been well studied. In some cases, researchers have examined how cooperative relationships can be influenced by agents that exhibit detailed facial expressions on a screen. It remains unclear whether and how expressive whole-body movements of real humanoid robots influence cooperative decision-making. To explore this, we conducted an experiment in which participants played a finite iterated prisoner’s dilemma game with a small humanoid robot that exhibits multimodal emotional expressions through limb motions, LED lights, and speech. Results showed that participants were more cooperative when the humanoid robot showed emotional expression. This implies that real humanoid robots that lack ability to show sophisticated facial expressions can form cooperative relationships with humans by using whole-body motion, colors, and speech.

机器人中的情感表现力吸引了越来越多的研究兴趣，并且近年来该技术的发展也取得了进步。已经提出了使用面部表情，语音，身体动作和指示情绪表情的颜色的多种方法。尽管先前的研究探索了情感表达如何被识别并影响人类行为，但是对合作和竞争性人机关系的研究还不够深入。在某些情况下，研究人员研究了在屏幕上展现详细面部表情的媒介如何影响合作关系。尚不清楚真正的类人机器人的全身运动是否以及如何影响整体决策。为了探索这一点，我们进行了一项实验，其中参与者使用小型人形机器人玩了有限的迭代囚徒困境游戏，该机器人通过肢体动作，LED灯和语音展示了多模态的情感表达。结果表明，当人形机器人表现出情感表达时，参与者更加合作。这意味着缺乏表达复杂面部表情能力的真实人形机器人可以通过使用全身运动，颜色和语音与人类形成合作关系。