Science has just published two short papers where researchers induced a touch sensation that that seemed to be felt in a ‘fake’ body that appeared to be several metres in front – similar to an ‘out-of-body-experience’.
The two studies were developed independently but both involved the same idea. In one study, the person was filmed from behind while they had their back stroked. They also wore a special head-mounted display that showed them what the video camera saw.
In other words, they saw their back being stroked as if they were sitting behind themselves and their body was in front of them. After a while, the sensation seemed to be move from their own back to be located in the projected body in front.
The other study did something very similar but used touches to the chest.
While these two studies have demonstrated the effect in a most striking way, the effect isn’t new, as it’s often been demonstrated with the ‘rubber hand illusion‘.
In fact, you can do something similar at home, and make touch sensations seem as if they are located in inanimate objects:
This is taken from Hack #64 (‘Mold your Body Schema’ [pdf]) from the Mind Hacks book, but was originally inspired by a similar exercise in Ramanchandran and Blakesee’s book Phantoms in the Brain:
Sit at a table with a friend at your side. Put one hand on your knee, out of sight under the table. Your friend‚Äôs job is to tap, touch, and stoke your hidden hand and‚Äîwith identical movements using her other hand‚Äîto tap the top of the table directly above. Do this for a couple of minutes. It helps if you concentrate on the table where your friend is touching, and it’s important you don’t get hints of how your friend is touching your hidden hand. The more irregular the pattern and the better synchronized the movements on your hand and on the table, the greater the chance this will work for you. About 50% of people begin to feel as if the tapping sensation is arising from the table, where they can see the tapping happening before their very eyes. If you’re lucky, the simultaneous touching and visual input have led the table to be incorporated into your body image.
All of these experiments synchronise the touch with visual movement, but put these perceptions in conflict with visual information about where the synchronisation is happening.
The brain attempts to resolve this conflict by prioritising the visual system, which is relatively information rich in comparison to our other senses.
Notably, these new studies are the first to demonstrate something akin to an ‘out-of-body-experience’.
It’s not really the same as the classic experience where you see your body in front of you, perhaps as you float above it, something known as autoscopy or heautoscopy in the medical literature.
However, as we reported last year, Prof Olaf Blanke’s team have studied various types of ‘out-of-body’ and ‘projected self’ experiences, either caused by direct brain stimulation, or after neurological disorder.
The lab’s publications page has many of their papers available as full-text articles if you want more detail.