In a virtual space such as the Metaverse, the experiencer wears an avatar of their choice and freely manipulates a "second body" with a high degree of spatial freedom.In particular, if the avatar's fingers and limbs can be transformed while maintaining the reality of the body, the operability of the virtual space will be enhanced.Therefore, it is an important issue to determine how much deformation each part of the body can psychologically withstand.

　In 2021, the research group announced the ``slime hand illusion,'' in which the skin of the hand is pinched and pulled, and at the same time, the mirror image of the slime is stretched in the same direction, giving the illusion of an extremely stretched skin. In the 2022 public experiment, 96% of the participants (95 out of 91) felt a strong sensation of skin stretch.

　In the subsequent on-campus experiment, 86% of the experiment participants strongly felt the stretching sensation of the skin, but 77% of the experiment participants strongly denied the sensation of moving the hand itself.Furthermore, when measuring the subjective position changes of each part of the body, the maximum displacement of the skin tip of about 40 cm was recorded on average for a slime deformation movement of 29 cm, but the displacement of the little finger position was average. and was about 11 cm.

　The results of this research strongly suggest that the "body as skin" can expand and contract farther than the "body as a skeleton", and it is said that it will force us to reexamine the spatial limitations that have been assumed in illusion research.It shows the possibility of boldly transforming the body of an avatar in the Metaverse space, and provides basic knowledge for future industrial applications.

Paper information:[i-Perception] The slime hand illusion: Nonproprioceptive ownership distortion specific to the skin region