November 18, 2023
For several decades the high-fidelity simulation realm of virtual reality (VR) has been the go-to tool for pyschophysicists and neuroscientists trying to uncover the mysteries of sensory processing and human perception. Researchers using VR have made a new discovery somewhat poetically called the "Phantom Touch Illusion" (PTI). In effect they have demonstrated that it is possible to feel real physical sensations based on how virtual elements interact. Here we’ll highlight the study findings and shed some light on the intricate workings of multisensory representation.
Inspired by the notion that you cannot tickle yourself due to tactile gating, German scientists at Ruhr-UniversityBochum employed immersive VR scenarios to investigate if seeing avatar representations of people could stimulate real physical sensations when asking them to touch parts of the avatar's body with a virtual stick.
Unexpectedly most participants reported a strong sensation manifested as a tingling or static feeling, akin to wind passing through the hand, corresponding to the specific location touched on the virtual body.
The intensity of the effects varied,with some of the people in the study believing the researchers were trying to trick them and were actually using some form of real tactile stimulation.
The study involved 36 subjects, with all but four reporting the PTI when using a virtual stick on their hands. Most strikingly, the sensation occurred even when subjects touched non-visible parts of their limbs. This finding suggests that the representation of one's body is defined top-down, extending beyond available sensory information.
The findings are distinct from the famous 'Rubber HandIllusion', which although equally fascinating, is an embodiment illusion, meaning people can perceive things not part of their own body to feel like their own body. However this relies on real tactile stimulation in order to induce the effect.
The discovery of the PTI alongside the Rubber Hand Illusion deepens our understanding of just how incredibly flexible the human mind is in how it determines the boundaries of physical and metaphysical perception. As researchers have established, this only occurs under very specific perceptual conditions which essentially 'make sense' to the brain.
A key point here is that VR technologies are ideal methods to simulate these types of powerful illusions and they are becoming increasingly sophisticated and affordable. High-fidelity virtual simulations today can be achieved with all-in-one VR headsets for as a little as $300, whereas 15 years ago the same level of simulation cost more inthe realm of $3m, and required serious technical expertise.
This makes replicating such studies or delving into more exploratory research in this domain highly accessible for neuroscientists, as well as having increasing relevance due to the public rise in adoption of VR for entertainment.
Although VR hardware technology has reached maturity in recent years, VR software development still has a long way to go, particularly as neuroscience expertise is required to design truly immersive simulations.
The fact that powerful physical illusions can be triggered with this form of technology means that VR has the potential to deliver next-level immersive experiences. For example imagine playing an avatar-based game and feeling physical sensations emanating from within the game world.
The Phantom Touch Illusion brings the discovery that human tactile perception occurs via top-down modulation of the somatosensory cortex through a very flexible body schema. It reveals anexciting new dimension in the immersive world of virtual reality, demonstrating much broader conceptions about self-touch and sensory perception in general.
Open-access study in Nature ScientificReports:
Artur Pilacinski, Marita Metzler &Christian Klaes.
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