In a typical experiment, a volunteer is being stroked while wearing a virtual reality headset. She’s lyng down and looking at her feet, but she doesn’t see them. Instead, the headset shows her the legs of a mannequin lying next to her.
As she watches, Bjorn van der Hoort, one of Ehrsson’s former interns, uses two rods to stroke her leg, and the leg of the mannequin, at the same time. This simple trick creates an overwhelming feeling that the mannequin’s legs are her own. If the legs belong to a Barbie, she feels like she’s the size of a doll. If the legs are huge, she feels like a 13-foot giant.
Van der Hoort performed this illusion on almost 200 people. Questionnaires revealed that they did indeed think of the mannequins as their own body parts. Familiar objects didn’t break the spell. When van der Hoort threatened the mannequins’ legs with a knife, the volunteers’ skin broke into a worried sweat, as if their real bodies were in danger. If he touched the doll’s legs with a pencil or his finger, the recruits thought they were being prodded by giant objects. Rather than feeling like dolls in a normal world, they felt like normal people in a giant world.
The researchers Not Exactly Rocket Science dub this the ‘Alice illusion’ after the changes in size experienced by the heroine in Alice in Wonderland.
These experiences can also be experienced as part of ‘Alice in Wonderland Syndrome’ which is usually associated with migraines or epilepsy (although they can occur without any brain disorder) likely due to them affecting the brain’s system for understanding the body’s relation to the surrounding space.
Temporary body-warping experiences are being created in the lab, however, in healthy normal folks and with surprisingly simple tricks.
The Not Exactly Rocket Science piece covers the latest delightful example.
Link to NERS on the ‘Alice illusion’.
Link to full text of scientific study.
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