Cross-Cultural Variation in Dishonesty Toward Humans and Artificial Agents Depends on Agent Pupil Size

As artificial agents become more involved in social and economic interactions that rely on honest behavior from humans, they are increasingly designed with human-like social cues—such as pupil size—to appear more approachable. Pupil size is subtle, but also a powerful cue that can guide our decisions. Yet, we still know little about how pupil size shape people’s behavior, especially across cultures where agents and their signals are interpreted and accepted differently. In this study, 275 participants from Europe and Japan played a coin toss game where lying increased financial gain. They interacted with a human confederate, a virtual avatar, or a robot. Agents' pupil sizes were manipulated to appear large or small; for human confederates, this was achieved using custom-designed contact lenses. Our results suggest that cultures differ in how dishonest behavior is directed toward human and artificial agents, with subtle social cues like pupil size influencing dishonesty in culture-specific ways. Despite these behavioral differences, physiological responses revealed similar patterns of arousal across cultures and agent types, indicating a shared implicit sensitivity to social presence. These findings highlight the need to consider cultural context when designing artificial agents that use human-like cues to guide social behavior: what subtly communicates warmth in one culture may signal something else in another.