Invisible Long Arm Illusion: Illusory Body Ownership by Synchronous Movement of Hands and Feet

Abstract

We feel as if a fake body is our own body by synchronicity between the fake body and the actual body (illusory body ownership) even if the body has a different shape. In our previous study, we showed that illusory body ownership can be induced to an invisible body through the synchronous movement of just the hands and feet. In this study, we investigated whether illusory body ownership can be induced to the invisible body even when the arm length of the invisible body was different from the usual body. We modified the length of arm of a full body avatar or changed the position of the hand of the invisible body stimulus, and found that the illusory body ownership was induced to the transformed body by synchronous movement. Participants' reaching behavior gradually changed to use the longer arm more during the learning of the transformed body.