Influence of Top-Down Interpretations on Visuo-Tactile Integration in Full-Body Illusion: Examination of the Relationship Between the Observer-Self and Self-Body

The full-body illusion (FBI) demonstrates the malleability of body ownership through multisensory integration. While bottom-up processes are well-documented, the role of top-down predictions remains unclear. Based on the predictive coding theory, we examined how different interpretive frameworks for the observer-self and virtual body relationship influence FBI strength. Sixty-six participants underwent a virtual reality FBI paradigm with synchronous/asynchronous visuo-tactile stimulation after being instructed to interpret the virtual body as either integrated with (integration condition) or separate from (separation condition) their physical body. Both groups received the fundamental instruction to “consider the virtual body as your own body.” Contrary to our hypothesis, no significant group × synchrony interaction emerged for either skin conductance responses or questionnaire measures, although exploratory analyses suggested potential group-specific patterns warranting future investigation. These findings suggest that fundamental ownership attributions dominate over conceptual distinctions, and that the precision of sensory evidence may outweigh subtle top-down modulations in body ownership, consistent with hierarchical predictive coding accounts of embodiment.