Social rather than physical crowding reduces the required interpersonal distance in virtual environments.

Interpersonal distance plays an important role in human social interaction. With the increasing usage of virtual reality in social interaction, people's interpersonal distance in virtual space attracts great attention. It remains unclear whether and to what extent human-required interpersonal distance is altered by crowded virtual scenes. In this study, we manipulated crowd density in virtual environments and used the classical stop-distance paradigm to measure required interpersonal distances at different crowd densities. We found that people's required interpersonal distance decreased with increased social crowdedness but not with physical crowdedness. Moreover, the decrease of two types of interpersonal distance was associated with the globally averaged crowd density rather than local crowd density. The reduction is not due to the imitation of other virtual humans in the crowd. Moreover, we developed a model to describe the quantitative relationships between the crowdedness of the environment and the required interpersonal distance. Our finding provides insights into designing user-friendly virtual humans in metaverse virtual worlds.