A study by the Sackler Centre for Consciousness Science found that a virtual-reality hand set to pulse in time to the beat of a heart creates the illusion of body ownership – the brain believes that the virtual hand is part of its own body.
Easily hoodwinked, the brain was first proved to accept a foreign hand as its own in 2009 in the now classic “rubber hand illusion.” The easily re-created trickery involved a blown up washing up glove, and a feather. With the rubber hand out of sight and only the sensory stimuli to go by, the brain soon perceived the rubber hand as part of the body as the hand was stroked at the same time as the real hand.
The experiment by Dr. Keisuke Suzuki and Prof. Anil Seth, was a virtual reality version of the rubber hand illusion and further explored the foundations of “proprioception” – the human cocktail of sense, touch and brain signals which create the experience of being in the body – the very foundation of self consciousness.
The researchers added a “cardio” element to the “rubber hand” illusion by using a unique combination of heartbeat monitoring and augmented reality which created a “cardio-visual” version of the rubber hand illusion.
21 volunteers participated in the study, involving the following steps:
- Participants wore a head-mounted display to facilitate the augmented reality in front of them
- The participants’ real hand was hidden from their visual field and attention drawn instead to the cardio-visual hand
- A virtual-reality, cardio-visual version of the participants’ own hands was projected onto a screen in front of them
- The cardio-virtual hand pulsed from red to black in time with the participants’ own heartbeats.
Results showed that the participants experienced the virtual hand as part of their body more frequently when the pulses were synchronized with their actual heartbeat, compared with when the pulses were out of synch.
The results show that the brain incorporates its impression of the body externally into its impression internally when determining what is actually happening to the body.
The experiment also showed that the accurate visual feedback of intentional hand movements provides a powerful prompt for the experience of body ownership that can surpass the influence of cardio-visual feedback.
The new findings, published in Neuropsychologia could lead to developments in the treatment of anxiety and body image disorders. If the body can trick itself into believing a rubber hand is its own, then perhaps it can believe a normal equilibrium of well being when before there was none.
Prof. Anil Seth says:
“The findings tie in with our research at the Sackler Centre showing that many other perceptual and cognitive processes can be affected by the beating of the heart in ways that have important implications for clinical conditions such as anxiety and disorders of body image.
Our results showed that the illusional experience of the body is associated with the individual interoceptive sensitivity (sensitivity to stimuli originating inside of the body). Although this sensitivity is not easy to be trained, it was reported that meditation possibly changes the interoceptive representation in our brain. As used in this study, experiencing the own heartbeat in visually salient ways might influence people’s interoceptive perception, which may help the anxiety disorder patients caused by the low interoceptive sensitivity.”
Press Release: Sussex University, Sackler Centre for Consciousness Science
Create your own “rubber hand” illusion (New Scientist)
Image credit: thanks to Mzacha of RGB Freestock