Hierarchical and dynamic relationships between body part ownership and full-body ownership

What is the relationship between experiencing individual body parts and the whole body as one’s own? We theorised that body part ownership is driven primarily by perceptual binding of visual and somatosensory signals from specific body parts, whereas full-body ownership depends on a more global binding process based on multisensory information from several body segments. To examine this hypothesis, we used a bodily illusion where participants rated illusory changes in ownership over five different parts of a mannequin’s body and the mannequin as a whole, while we manipulated the synchrony or asynchrony of visual and tactile stimuli delivered to three different body parts. We found that body part ownership was driven primarily by local visuotactile synchrony and could be experienced relatively independently of full-body ownership. Full-body ownership depended on the number of synchronously stimulated parts in a non-linear manner with the strongest full-body ownership illusion elicited when all parts received synchronous stimulation. Additionally, full-body ownership influenced body part ownership for non-stimulated body parts, and skin-conductance responses provided physiological evidence for an interaction between part and full-body ownership. We conclude that part and full-body ownership correspond to different processes and propose a hierarchical probabilistic model to explain the relationship between part and whole in multisensory awareness of one’s own body.