More rubber body parts

A few weeks ago I wrote about experiments being conducted at Vanderbilt University. The original article appeared in Discover Magazine. In this well-known experiment dating back to a Princeton University party game, a rubber hand is introduced and stroked in time with one of the volunteer's hands while the other hand is hidden under a table. The findings of the Vanderbilt study confirmed its premise that people with psychotic episodes have a weaker sense of self and therefore experienced the illusion more strongly than people of a similar age and background who didn’t have schizophrenia.

Try this, Descartes!

This month's Nature Magazine has an article on neurologist Henrik Ehrsson's research. While what is going on in the laboratory makes for most interesting reading, there is enormous danger with these kinds of experiments done in the name of scientific progress because of the dark science of mind and body control of another human being. Read the article below. See what you think.

It is not every day that you are separated from your body and then stabbed in the chest with a kitchen knife.

But such experiences are routine in the lab of Henrik Ehrsson, a neuroscientist at the Karolinska Institute in Stockholm, who uses illusions to probe, stretch and displace people's sense of self. Today, using little more than a video camera, goggles and two sticks, he has convinced me that I am floating a few metres behind my own body. As I see a knife plunging towards my virtual chest, I flinch. Two electrodes on my fingers record the sweat that automatically erupts on my skin, and a nearby laptop plots my spiking fear on a graph.

Out-of-body experiences are just part of Ehrsson's repertoire. He has convinced people that they have swapped bodies with another person1, gained a third arm2, shrunk to the size of a doll or grown to giant proportions3. The storeroom in his lab is stuffed with mannequins of various sizes, disembodied dolls' heads, fake hands, cameras, knives and hammers. It looks like a serial killer's basement. “The other neuroscientists think we're a little crazy,” Ehrsson admits.

But Ehrsson's unorthodox apparatus amount to more than cheap trickery. They are part of his quest to understand how people come to experience a sense of self, located within their own bodies. The feeling of body ownership is so ingrained that few people ever think about it — and those scientists and philosophers who do have assumed that it was unassailable.

“Descartes said that if there's something you can be certain of in this world, it's that your hand is your hand,” says Ehrsson. Yet Ehrsson's illusions have shown that such certainties, built on a lifetime of experience, can be disrupted with just ten seconds of visual and tactile deception. This surprising malleability suggests that the brain continuously constructs its feeling of body ownership using information from the senses — a finding that has earned Ehrsson publications in Science and other top journals, along with the attention of other neuroscientists.

“A lot of people thought the sense of self was hard-wired, but it's not at all. It can be changed very quickly, and that's very intriguing,” says Miguel Nicolelis, a neurobiologist at Duke University Medical Center in Durham, North Carolina.

Ehrsson's work also intrigues neuroscientists and philosophers because it turns a slippery, metaphysical construct — the self — into something that scientists can dissect. “We can say if we wobble the signals this way, our conscious experience wobbles in this way,” says David Eagleman, a neuroscientist who studies perception at Baylor College of Medicine in Houston, Texas. “That's a lever we didn't have before.”

“There are things like selfhood that people think cannot be touched by the hard sciences,” says Thomas Metzinger, director of the Theoretical Philosophy Group at Johannes Gutenberg University of Mainz, Germany. “They are now demonstrably tractable. That's what I think is valuable about Henrik's contribution.”

Read the rest of the article here.