10 October 2016

More accurate estimate of hips and belly size in virtual world

Patients with anorexia have a persistently distorted body image. This means, for example, that they believe their belly and hips to be bigger than they actually are. Changing that body image is one of the challenges that experimental psychologist Anouk Keizer from Utrecht University has set herself. Using a virtual reality headset, with software developed by Ordina, she recently succeeded in enabling anorexia patients to make a more realistic estimate of their body size. Her findings have been published today in PLOS ONE.

Using a method similar to the ‘Rubber Hand Illusion’, where people start to experience a rubber hand as their own through contact with it, Keizer has created a Full Body Illusion. It is an illusion that encompasses the anorexia patient's entire body, in a virtual world. Keizer: “We know that, after the rubber hand illusion experiment, anorexia patients estimate the size of their own hand more accurately. What I now wanted to investigate was whether we can achieve something similar using body parts that they are concerned about and have always perceived as being too big: their hips and belly, for example.”

VR headset

The patients who took part were asked to wear a virtual reality headset. In the virtual world shown to them, they could see their virtual body. The researcher used a brush to stroke the participants' actual body parts. Simultaneously, they saw the same, virtual body parts also being touched with a brush. This created the Full Body Illusion.

Thinner estimate

Participants were asked to estimate the size of their belly and hips both before and after this illusion. After the illusion, the anorexia patients estimated the size of their body parts more realistically than before it. For some time – approximately three hours – after the Full Body Illusion, they still perceived their body parts to be thinner.

Extremely difficult

Keizer argues that this is an extraordinary finding. “It is extremely difficult to give anorexia patients a different perceived body image. This has now proved successful, even for body parts about which the patient is particularly concerned, such as the belly and hips.”
The experimental psychologist stresses that her research should not be seen as a fully-fledged therapy for patients. “It perhaps marks the first step for these patients in changing their body image.” Further research will also be required to identify the mechanism at work in this changed body experience.