Interpersonal Synchrony Affects the Full-Body Illusion

The full-body illusion (FBI) is a phenomenon where individuals experience body perception not in their physical body but in an external virtual body. Previous studies have shown that the relationship between the self and the virtual body influences the occurrence and intensity of the FBI. However, the influence of interpersonal factors on the FBI has not been explored. This study investigated the effect of interpersonal synchrony on body perception through an evaluation experiment involving the FBI. Specifically, the participant and an experimenter clapped together while their movements were recorded by a video camera placed behind the participant and displayed to them via a head-mounted display (HMD). This setup presented synchronous visuotactile stimuli, aligning the visual feedback with the tactile sensations in the participant’s hands, to induce the FBI. The experimenter’s clapping rhythm was manipulated to either be synchronous or asynchronous with the participant’s rhythm, thus controlling the state of movement synchronization between the participant and the experimenter. The impact on the participant’s body perception was then assessed through subjective reports. The results indicated that when the clapping rhythm was synchronized with the other person, there was a significant reduction in touch referral to the participant’s virtual body. Additionally, there was a trend toward a reduction in ownership. This study demonstrated for the first time that interpersonal synchrony affects body perception.