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It’s Behind You! Robot Creates Ghostly Presence on Demand

Researchers have created a robotic system that makes people feel as if a ghostly presence is standing behind them in the room, simply by turning their own movements into mixed-up sensory feedback. The experiment, detailed Thursday in Current Biology, builds upon previous studies of out-of-body experiences. "Thirty percent of the healthy participants spontaneously reported the feeling of having somebody behind them, touching them," Olaf Blanke of Switzerland's Ecole Polytechnique Federale de Lausanne, or EPFL, said in a news release. Two of them were so freaked out they wanted to stop the experiment.

The system was hooked up so that blindfolded participants used their finger to operate a master-slave robot with a mechanical finger that touched their backs in return. When the robot's touch went out of phase with the body movements, some subjects felt as if they were being touched by someone behind them — and in some cases, as if they were drifting backward toward the ghostly presence. The researchers said the subjects generated the illusion to resolve the "spatiotemporal conflict" they were experiencing. They suggested the findings could help explain mystical experiences as well as schizophrenic hallucinations.

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In addition to Blanke, the authors of "Neurological and Robot-Controlled Induction of an Apparition" include Polona Pozeg, Masayuki Hara, Lukas Heydrich, Andrea Serino, Akio Yamamoto, Toshiro Higuchi, Roy Salomon, Margitta Seeck, Theodor Landis, Shahar Arzy, Bruno Herbelin, Hannes Bleuler and Giulio Rognini.