A link between hypnotic suggestibility and body image: why some people 'misplace' their own hand
Posted on 21/08/2015
People who score highly on a test of hypnotic suggestibility are more susceptible to the so-called ‘rubber hand illusion’, according to new research from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London. The research offers insights into why some people are more likely than others to ‘misplace’ their own hand during this fascinating illusion.
The rubber hand illusion is a classic research paradigm used to investigate body ownership, awareness and body image. In the paradigm, participants view a rubber hand being stroked simultaneously with their own adjacent hand which is hidden from their view. They can therefore see the rubber hand being stroked, and at the same time feel their own hidden hand being brushed. After a few minutes of stroking, most people begin to perceptually ‘incorporate’ the rubber hand into their own body, and report that “it feels as if the rubber hand is my hand”.
In the research published in the journal Perception, twenty-three participants were assessed for hypnotic suggestibility using the Harvard Group Scale. Hypnotic suggestibility refers to a person’s ability to experience alterations in sensations, emotions, thoughts, or behaviour in response to suggestions following hypnosis. Most people are hypnotisable to some extent, and one in ten of us is ‘highly hypnotisable.’ Much like a personality trait, hypnotic suggestibility remains stable across the lifespan.
The researchers examined the link between the Harvard Group Scale and two different aspects of the rubber hand illusion. First, a questionnaire measured how strongly people felt that “the rubber hand was my hand.” Second, participants were asked to estimate the position of their right hand which is hidden from their view. The researchers found that during the illusion, hypnotisable people are much more likely to report their actual hand as being closer to the rubber hand than it really is.
Dr Eamonn Walsh says: ‘Most of our participants reported experiencing a strong illusion regardless of whether they are hypnotizable or not. Interestingly, we found that the more hypnotizable someone is, the more likely they are to misestimate the actual position of their own hand, and in the direction of the rubber hand. This may due to the greater attentional focus hypnotisable people can bring to bear on a stimulus, such as a rubber hand, thereby leading to a more intense illusion. This finding is important as it demonstrates a clear link between hypnotic suggestibility and body image.’
Dr Quinton Deeley, Consultant Psychiatrist and Senior Lecturer in Social Behaviour and Neurodevelopment, says: ‘Body image is an important and underresearched area. Strategies based around the rubber hand illusion and this principle of altering perception of our body image could help amputees, people with body image disorders and stroke victims. For example, touching an amputee’s stump while they look at the prosthesis in place of their missing limb can help them feel that they ‘own’ their prosthesis, enabling them to control it better.’
Dr Mitul Mehta, Reader in Imaging & Psychopharmacology, adds: ‘We are beginning to understand the brain basis of hypnotic suggestibility using verbal suggestion. Importantly, our study shows that the hypnotisabilty trait is related to the response to non-verbal suggestions, such as in the rubber hand illusion. Insights into individual differences in responding to non-verbal suggestions may help us understand the causes and the treatment of neuropsychiatric symptoms.’
Notes to editors
Paper reference: Walsh, E., Guilmette, D.N., Longo, M.R., Moore, J.W., Oakley, D. A., Halligan, P. W., Mehta, M.A., & Deeley, Q. (2015). Are you suggesting that’s my hand? The relation between hypnotic suggestibility and the rubber hand illusion. Perception.
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