Scientists at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have designed a robot that causes the brain to believe that a "ghostly presence" is standing directly behind and uncomfortably close to a subject, Scientific American reports.
The robot produces what researchers call the "Feeling of Presence," the disturbing feeling that someone is hovering alongside or next to an individual, which is a common symptom in neurological conditions like schizophrenia and Alzheimer's.
According to the paper in the most recent issue of Current Biology, the Swiss scientists have been able to replicate the phenomenon in neurologically healthy individuals.
"You really need a sensorimotor mismatch for Feeling of Presence,” EPFL scientist Giulio Rognini said.
In order to create this mismatch, the scientists built a robot that exactly mimicked the movements of blindfolded subjects. When the subject reached forward, the robot would reach forward too -- and touch the subject on the back. When the movements were synchronized, the subject would report that they were touching themselves on their own backs.
But when the scientists delayed the robot's movements by as little as one half-second, the subjects were immediately disoriented -- they claimed they felt as if they were drifting backward, towards some unknown presence, or that the empty room behind them was full of people.
This it because "the illusion of feeling another person nearby is caused by misperceiving the source and identity of sensorimotor -- tactile, proprioceptive, and motor -- signals of one’s own body."
"What we are doing is manipulating those sensorimotor signals,” Rognini said. “We found that [Feeling of Presence] is only experienced when there is a delay between what participants do and a feeling on their backs."
"Our findings," the researchers wrote, "reveal the neural mechanisms of the [Feelings of Presence], and highlight the subtle balance of brain mechanisms that generate the experience of 'self' and 'other.'"
Their long-term goal is to design a robot that will help schizophrenics reconnect with their own bodies by retraining how their brains to correctly interpret the "Feeling of Presence."
Watch a video about the "Feeling of Presence" phenomenon via EPFL News on YouTube below.