How the Body Transfer Illusion Tricks Your Brain
Our sense of self is more flexible than we think. Learn how the brain can be persuaded to experience an artificial body as its own through sensory signals.
The body transfer illusion is a perceptual phenomenon where an individual experiences an artificial body part or an entire foreign body as their own, demonstrating that our sense of body ownership is not fixed. This illusion occurs when the brain’s interpretation of sensory information overrides the logical knowledge that a particular body is not one’s own. The experience can be so convincing that a person might feel sensations originating from a mannequin’s hand or an avatar’s body.
Methods for Inducing the Illusion
The foundational method for studying this phenomenon is the “rubber hand illusion.” In this setup, a participant’s real hand is hidden from their view, and a realistic rubber hand is placed in front of them. An experimenter then uses two small paintbrushes to simultaneously stroke the participant’s hidden hand and the visible rubber hand. When the stroking is synchronous, participants often report feeling the sensation in the rubber hand, as if it were their own.
This concept extends to full-body illusions using a mannequin and cameras. A participant wears a head-mounted display showing a live feed from cameras on the mannequin’s head, giving them a first-person perspective of its body. An experimenter applies identical, synchronized touches to both the participant’s hidden body and the mannequin’s visible body. This creates the feeling that the mannequin’s body is their own.
The timing of sensory inputs is a primary factor in creating the illusion. If the touch on the real and fake body is asynchronous, the illusion is significantly reduced or fails to occur. Modern approaches use immersive virtual reality (VR) to generate these illusions, allowing participants to embody a digital avatar. VR provides a controlled environment for manipulating sensory feedback and studying the experience.
How the Brain Perceives the Body
The body transfer illusion occurs through multisensory integration, a process where the brain combines information from different senses to form a coherent perception. Vision, touch, and proprioception—the internal sense of our body’s position—all contribute to our sense of self. During the illusion, the brain receives conflicting signals, as proprioception indicates the real limb’s location while vision shows the artificial one.
When visual and tactile inputs are synchronized, vision often dominates the other senses. The brain resolves this conflict by accepting the visual information as correct and referring the feeling of touch to the artificial limb’s location. This process effectively recalibrates the brain’s map of the body in space.
Several brain regions are involved in this integration. The premotor cortex, which plans movements and represents the space near the body, shows increased activity during the illusion. The intraparietal cortex helps integrate sensory inputs from different modalities. Activity in the temporoparietal junction is also associated with distinguishing self from other, helping the brain adopt the new body representation.
Implications for Science and Medicine
Body transfer illusion research has practical applications, particularly in developing advanced prosthetics. By understanding how the brain adopts an artificial limb, engineers can design prosthetics that users feel are a genuine part of their body. This enhanced sense of ownership can improve motor control and make the prosthetic feel less like a foreign object.
The illusion has therapeutic uses, especially through virtual reality. It is explored as a treatment for phantom limb pain, where amputees feel pain in a missing limb. By embodying a virtual avatar with a complete body, patients receive visual feedback of the “missing” limb being touched, which can alleviate their pain. It also shows potential for treating body dysmorphic disorders by allowing individuals to temporarily experience a different body, altering their self-perception.
These illusions contribute to questions about consciousness and the mind-body relationship. They show that the sense of self is continuously constructed based on sensory input. By manipulating body perception in a controlled setting, scientists can explore the boundaries of self-awareness and what it means to have a body.