Walking into a darkened room you feel them standing behind you, just out of sight, breathing down your neck. You jump around, no-ones there. What you’ve just experienced is called feeling of a presence (FoP), and you’re not the only one. Legends of ghosts, spirits and other such ethereal presences have been found in almost all cultures across the centuries.
But how do these presences come about and can we generate these feelings in experimental conditions? That is what scientists, led by Giulio Rogini at the Swiss federal institute of technology, have been investigating in a recent article published in Current Biology
The researchers were able to investigate this using a robotic system, the subjects controlled a robot using their finger inserted in a mechanism which controlled a robotic finger located behind the subject. Whilst blindfolded the subject moved their own finger and the robotic finger imitated this movement, touching the back of the subject. All the test subjects were aware of how the machine functioned and none knew they were meant to experience anything creepy. When the patient’s movements were in sync with the robot nothing unusual was reported, subjects experienced the feeling of touching their own backs, despite their arm being in front of them.
Ghost. Source: pixabay.com
However, when the robot’s movements were made “Asynchronous” (delayed by 5 seconds) things started to get spooky, many subjects reported the feeling that someone was standing behind them, two subjects were made so uncomfortable they asked to be allowed to stop. Many subjects unconsciously began to drift backwards towards this imagined presence. When asked how many people had been in the room, close to the subject, almost all subjects paired with an out of synch robot counted extra people, on average one more than those who had a synchronous robot.
“Several of them really did say the sensation was spooky and creepy, even though consciously they knew where the touching came from,” Rognini says.The researchers concluded that the “feeling of a presence” reported by the subjects was bought about by the conflicting sensorimotor signals being experienced.The fact that the experienced signals were spatially and temporarily incompatible was resolved in the brain of a subject by the presence of another person in the room who was responsible for touching the subjects back.
‘the results of the study go far towards explaining an interesting cultural phenomenon but also have huge relevance with regards to the study of schizophrenia.’
Such reductions in self-touch and agency for one’s actions have been reported before with respects to visual-motor and audio-motor conflicts.The results of the study go far towards explaining an interesting cultural phenomenon but also have huge relevance with regards to the study of schizophrenia. It may be the case that schizophrenic symptoms are caused by abnormalities in the integration of sensorimotor signals and their respective cortical representations.
Ghost in Alley. source: pixabay.com
Schizophrenic symptoms such as voices and delusions of control, may be caused by deficits in integrating the predicted sensory consequences of one’s own movement, schizophrenic patients under certain conditions may not perceive self-generated sounds and movements as such, but may misperceive them as being generated by an external agent.This data may account for a loss of agency in such patients and also shows that a conflict between motor signals and tactile feedback at a physically impossible position results in the feeling of being in the presence of a foreign agent and being touched by that invisible person.
Feeling of Presence is a cultural phenomenon that has fascinated mankind since time immemorial, and has had an impact on many areas of society, from the stories told around campfires to modern day horror films. This study provides important information in understanding the phenomenon as well as leading to a greater understanding of complex neurological diseases such as schizophrenia.
