Effect of a Body Part Action on Body Perception of the Other Inactive Body Part

Abstract

The rubber hand illusion (RHI) is an illusory experience in which a fake rubber hand is felt as if it were one's own hand when the visible fake and invisible real hands are stimulated synchronously. Although several studies have suggested contributions of action to body ownership using the RHI paradigm, the relationship between body ownership and agency has not yet been fully revealed. To better understand this relationship, the present study investigated the transfer of body ownership between body parts induced by a body part action. Using an RHI paradigm involving virtual reality, we tested whether a simple finger action of the dominant (active) hand can induce the embodiment of a virtual hand corresponding to the non-dominant (inactive) hand. We evaluated the illusory experience, perceptual changes, and physiological changes during the experiment with a subjective questionnaire, crossmodal congruency effect measurement, and skin temperature measurement, respectively. The results demonstrated that the finger action induced the embodiment of both virtual hands, causing a significant increase in agency of the inactive hand. This suggests that the illusory experience induced by an active body part contributes to an increase in agency as well as body ownership over the virtual body of the other inactive body part.Index Terms-Rubber hand illusion, virtual hand illusion, sense of body ownership, sense of agency, cognetics. I. INTRODUCTIONI N general, humans never doubt a sense of "my body (or body part) belongs to me" (i.e., the sense of body ownership) or "I am moving (or controlling) my body" (i.e., the sense of agency) [1] although they are not particularly aware in daily life. For instance, we never consider that our fingers and hands are tools or being moved by someone else when we play a piano or type at a keyboard by ourselves. Such awareness is normally robust, but could deteriorate in higher brain dysfunction or psychiatric/neurological disorders.

Neural Substrates of Body Ownership and Agency during Voluntary Movement

“…In line with this, post hoc pairwise comparisons between the A M S T C O and P M S T C O conditions in terms of ownership index ( t = 3.155; df = 29; p = 0.004; Cohen's d = 0.607) and ownership scores ( t = 2.413; df = 29; p = 0.023; Cohen's d = 0.464) further revealed significant differences in both cases. This is an interesting behavioral finding that suggests that active finger movements provide a stronger cue for body ownership than passive finger movements, which has a bearing on an ongoing debate in the behavioral literature on whether body ownership and agency interact in the moving rubber hand illusion or if they are completely independent ( Dummer et al, 2009 ; Tsakiris et al, 2010 ; Walsh et al, 2011 ; Kalckert and Ehrsson, 2012 , 2014 , 2017 ; Riemer et al, 2013 ; Hara et al, 2022 ).…”