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This Robot Makes You Feel Like There Is a Ghost behind You

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Image credit: Researchers have successfully devised a robot capable of giving otherwise healthy people that “feeling of a presence” (FoP) phenomenon, simply by sending mixed-up sensorimotor signals to the brain / Alain Herzog/EPFL

Do you have the experience of feeling a ghost in your room? After studying several patients with neurological conditions scientists confirmed that they had identified where the phenomenon of such feeling came from. Therefore, they did build a robot that could be bale to recreate that very same feeling by the means of transmitting mixed-up sensory and motor signals to the brain. Their research had been published in the recent edition of Current Biology.

Olaf Blanke and his team from the Ecole Polytechnique Fédérale de Lausanne were engaged in experiments of twelve patients with epilepsy, migraine, stroke and tumors. Due to potential damage, sometimes such patients could perceive invisible “presences” for seconds, even for minutes. By application of brain imaging, the researchers followed these misperceptions to damage in the three regions, such as the temporoparietal, insular, and frontoparietal cortex. In their finding, different brain lesions were closely linked with their own sensory and motor deficits. If the brain could not integrate different signals passed on by the limbs in a proper way, such spooky feeling would happen as a result. Being usually generated by touch, these signals would help people know about their position within the space and time.

Did healthy people also have such experience of feeling something to be present? The team had the doubt about it. They thought that the confusion over the source and identity of sensorimotor signals would be the main cause, because people would misattribute their own signals or bodily movements as something “other,” thus leading to the ghostly sensation. As Blanke said, people were often convinced that there should be something, but actually they failed to see anything or hear anything.

In order to test whether it was true or not, Blanke’s team built a “master-slave” robot system which enabled allowed them to apply sensorimotor conflicts which seemed to be physically impossible. For instance, the robot made it possible for the healthy recruits to feel as if they were reaching out before themselves and touching their own backs. That was because the blindfolded recruits could use their fingers and hands to move the arm of a master robot just before them, and at the same time another robot behind them would poke them through a similar movement.

However, if a half-second delay in the poke existed, the participants had the feeling that there should be someone (or something) just standing behind them.

According to Blanke, 30 percent of the healthy participants were naturally reported to have such feeling of getting somebody behind them as well as touching them. To solve the spatiotemporal conflict within their head, the recruits created the illusion that instead of being done by them, the touch was caused by the “other.” You can watch the participants using the robots here and here.

Some participants even began with the feeling like that their bodies were floating backward in space, toward the weird other. When the researchers tried to make some recruits believe that up to four people might be in the room together with them at the moment, the participants experiencing a delayed touch would respond they felt absolutely there were some people really in the room, even though in fact they were just alone with the robots.

During the experiment, two of the participants wanted to stop it because the robot-induced “presence” was very confusing to them.

These findings could be much helpful in explaining  schizophrenic hallucinations as well as phenomenon of “the third man” which often came to the mind of mountaineers.

Source: Eurekalert!, Nature, New Scientist

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