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Scientists Used Robots to Trick People into Sensing Ghosts

The finding explains why people with psychological disorders often feel eerie presences around them.
Image: Swiss Federal Institute of Technology

A recent study undertaken in Switzerland was so disconcerting that several participants asked researchers to stop the experiment because they were too scared. What were they scared of? Well, using a robot and some brain trickery, researchers successfully tricked people into thinking there were ghosts in the room with them.

The study, amazingly titled "Neurological and Robot-Controlled Induction of an Apparition," is one of the first to help us understand why and how people—specifically, those with psychological issues such as schizophrenia or people who are placed into extreme situations—start to perceive ghosts or, as the authors put it, the "feeling of a presence."

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"We had two participants who wanted to stop because it was so creepy," Giuilo Rognini, a researcher at the Swiss Federal Institute of Technology, told me. "What we were inducing is an illusory feeling. It's not a hallucination, they really feel there is somebody there."

To do this, Rognini set up what's called a "master / slave" robot system. Participants stood between these two robots and moved around the master robot for three minutes. The slave robot, which was positioned behind them, touched the participants in the back in a fashion that mirrored the master robot's movements.

This wasn't enough to create the feeling of a ghost being in the room, but it gave participants the feeling of touching their own backs. But then, when that synchronism was delayed, they began suggesting that other people were indeed in the room, when they actually weren't.

"There was a mismatch between what they do and what they feel," Rognini said. "It relates to phenomenon of what we've seen in psychiatric patients before. The presence is always perceived as unpleasant, and the emotional feeling that's related to that is never nice."

So, poking someone in the back doesn't exactly seem like a way of creating true (perceived) ghosts, at least not on its face. But, in 12 patients who have experienced feeling of presence (due to epilepsy or another disorder), the sensation described was extremely similar.

Beyond that, a mountain climber named Reinhold Messner once described the feeling of presence he experienced while descending Nanga Parbat with his brother in an extremely physically exhausted state. He felt a third climber "keeping a regular distance a little to my right and a few steps away from me, just outside my field of vision."

This experience suggests, according to Rognini's paper, published in Current Biology, that feeling of presence can often show up in people who are extremely exhausted.

But, perhaps most importantly, the study finds the underlying neurological basis for feeling the presence of ghosts. In brain scans done on healthy study participants, the researchers found that perceiving a ghost is simply an interference between three separate cortex regions in the brain, called the insular cortex, parietal-frontal cortex, and the temporo-parietal cortex. These three regions are responsible for self-awareness, movement, and the way you sense the space around you.

These regions were affected in the neurological patients and were also activated in the test participants, suggesting that when you feel a ghost, well, it's probably all in your head.