Scientists in Switzerland have managed to create the sensation of being watched and touched by "ghosts" in a controlled experiment, showing that they are probably just figments of our imagination.
In the two-part experiment at the Ecole Polytechnique Federale de Lausanne (EPFL), blindfolded volunteers controlled a robotic arm with their index fingers.
At first the volunteers and the robotic arm worked in sync, allowing them to experience the disconcerting feeling that they were stroking their own backs.
But when the movements of the robotic arm were delayed by about 500 milliseconds the participants reported seeing up to four ghosts around them and felt that the robotic finger stroking them belonged to an unseen presence.
One in three felt as if they were being watched or touched by the apparitions, while two were so disturbed that they begged for it to stop.
The researchers believe this is proof that ghosts or ‘feelings of presence’ (known as FOP) can arise when the brain's signals get confused and it briefly loses track of the body’s location.
This is most likely to happen because of stress, illness or grief, or in situations of intense exertion such as mountaineering.