Merging Bodies, Dividing Conflict: Body-Swapping in Mixed Reality Increases Closeness Yet Weakens the Joint Simon Effect

Mixed Reality (MR) presents novel opportunities to investigate how individuals perceive themselves and others during shared, augmented experiences within a common physical environment. Previous research has demonstrated that users can embody avatars in MR, temporarily extending their sense of self. However, there has been limited exploration of body-swapping, a condition in which two individuals simultaneously inhabit each other's avatars, and its potential effects on social interaction in immersive environments. To address this gap, we adapted the Joint Simon Task (JST), a well-established implicit paradigm, to examine how body-swapping influences the cognitive and perceptual boundaries between self and other. Our results indicate that body-swapping led participants to experience themselves and their partner as functioning like a single, unified system, as in two bodies operating as one agent. This suggests possible cognitive and perceptual changes that go beyond simple collaboration. Our findings have significant implications for the design of MR systems intended to support collaboration, empathy, social learning, and therapeutic interventions through shared embodiment.