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HOME > No.22, Sep. 2020 > Human’s sense of whole body ownership is partly dependent on spatial placement

Human’s sense of whole body ownership is partly dependent on spatial placement

Separation of body part ownership from body ownership using virtual scrambled body stimulationBy Ryota Kondo
Ryota Kondo

Differences between whole-body and body-part ownership were clarified using scrambled body stimulation in a virtual environment, wherein the hands and feet of the experiment’s participants were presented in randomized spatial arrangements. While moving, the scrambled body stimulation produces a sense of possession of limbs (hands and feet), but possession of the whole body cannot be grasped. Spatial placement is important for the illusion of whole-body ownership. Any individual’s sense of possessing their own bodies can thus be said to be affected by the body’s spatial arrangement.

A research team consisting of Ryota Kondo (Ph.D. candidate), Yamato Tani (Graduate student), and Professor Michiteru Kitazaki from Toyohashi University of Technology, Associate Professor Maki Sugimoto from Keio University, and Professor Masahiko Inami from The University of Tokyo investigated the difference between the sense of ownership of the whole body and the sense of ownership of body parts using scrambled body stimulation. Only the hands and feet of the experiment’s participants were presented, and their spatial arrangement was randomized. It was found that observing the scrambled body stimulus while moving the whole body produces a sense of possession of the body part with respect to the hands and feet, but did not create a sense of possession of the whole body. This result suggests that spatial arrangement is important for the illusion of whole-body ownership. In addition, individual sense of body self-possession may be affected by the spatial arrangement of one’s own body. The results of this study were published in the open access journal Scientific Reports on 24th March 2020.

Whole-body ownership is an important phenomenon to examine bodily self-consciousness. However, differences between our sense of ownership of body parts compared to ownership of the whole body are not completely understood as there has been no effective method to separate these senses of ownership.

Therefore, the research team aimed to develop a method to separate the ownership of body parts from the ownership of whole body. Based on their previous study (Kondo et al., Scientific Reports, 2018) on transparent body stimulation, a scrambled body stimulation that randomly rearranges the positions of hands and feet was conducted. Then, in order to compare it with the stimulus of the same arrangement as the normal body, synchronization with the physical movement was controlled.

Experimental participant (left), the corresponding normal placement stimulus (center), and the scrambled body stimulus (right).
Experimental participant (left), the corresponding normal placement stimulus (center), and the scrambled body stimulus (right).

In the first experiment, 16 volunteers observed limb-only stimuli from a third-person perspective (2m behind the stimuli) on a head-mounted display. As a result, when vision and physical movement were synchronized, scrambled body stimulation produced only a partial sense of body ownership (It felt as if only the virtual limbs were part of their body), whereas normal placement body stimulation produced both body-part ownership and whole-body ownership (it felt as if the space between the limbs was their body). Similar results were obtained in the second experiment, in which 16 participants observed the stimulus from a first-person perspective.

An example of a normal placement body stimulus synchronized with the movement of the experiment participant, followed by a scrambled body stimulus.

Thus, humans can feel ownership of certain body parts even if the body parts are scrambled, but cannot get a sense of whole-body ownership in this scenario. However, there was no significant difference in any of the skin conductance response measurement for threat stimuli in the third experiment, conducted with 20 participants.

These results suggest that a spatial placement is necessary for a sense of whole-body ownership, but not necessarily for body-part ownership. Therefore, a person’s whole body consciousness may be impacted by the spatial arrangement of certain body parts. However, the limitation of this study was that there was no difference in skin conductance (physiological) response to a threat stimulus.

Scrambled body stimulation provides a method to systematically examine the sense of ownership of the whole body and body parts. Moreover, it helps explore the limitations of the illusion of how much we can change our body scheme while retaining a feeling of whole-body ownership.

This research was supported by JST ERATO Grant Number JPMJER1701 (Inami JIZAI Body Project), and JSPS KAKENHI Grant Number P19J12660.


Kondo, R., Tani, Y., Sugimoto, M., Inami, M., and Kitazaki, M. (2020). Scrambled body differentiates body part ownership from the full body illusion. Scientific Reports, 10, DOI: 10.1038/s41598-020-62121-9


By 近藤 亮太


豊橋技術科学大学の大学院生である近藤亮太(日本学術振興会DC特別研究員)と谷大和、研究指導教員の北崎充晃教授、および慶應義塾大学の杉本麻樹准教授、東京大学の稲見昌彦教授による研究グループは、バーチャルリアリティ空間でのスクランブル身体刺激を用いて全身所有感と身体部位所有感の違いを明らかにしました。この研究成果は、2020年3月24日にScientific Reports誌に発表されました。

バーチャルリアリティを用いて、身体運動に同期させてバーチャルな身体の視覚映像を見せることで身体所有感の錯覚を生じさせることができます。研究グループは、2018年5月に手と足のみを提示して身体運動と同期させることで透明な身体を知覚させることができることを示しました(Kondo, et al., Scientific Reports, 2018)。その研究では、バーチャルな手と足に所有感を感じると同時に、それらを補間する身体全体に所有感が感じられました。






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Researcher Profile

Ryota Kondo
Name Ryota Kondo
Affiliation Department of Computer Science and Engineering
Title PhD student
Fields of Research Body Ownership, Agency, Out-of-body Experience, Human Augmentation, Virtual Reality