A robot inducing sensorimotor conflict reproduced the 'feeling of a presence' in healthy people, modeling a clinical hallucination

Roughly a decade after mapping out-of-body experiences to angular-gyrus stimulation (claim-angular-gyrus-stimulation-induced-out-of-body-experience), Blanke's group engineered the effect in neurologically healthy volunteers without touching cortex. Blindfolded subjects operated a master–slave robotic device that delivered spatiotemporally mismatched tactile feedback to their own back; the delay and displacement between the movement they made and the touch they felt induced a "feeling of a presence" (FoP) — the vivid, unshakeable sense that an unseen someone was standing nearby.

Crucially, this is not a novel laboratory curiosity but a reproduction of a real clinical symptom: FoP is "the same experience spontaneously described by neurological and psychiatric patients." The authors attribute it to the brain "misperceiving the source and identity of sensorimotor (tactile, proprioceptive, and motor) signals," and connect the mechanism to the sensorimotor account of hallucinations in schizophrenia — where signals the self generates are misattributed to an external agent.

The through-line with the 2002 result is a single mechanism at two levels of control: an integration failure that stimulation forces on one patient's cortex, an experimenter can instead manufacture on demand in anyone by feeding the sensorimotor loop conflicting evidence. The clinical name this laboratory FoP is popularly attached to — the "Third Man Factor" — has a literary rather than neuroscientific pedigree, traced in claim-third-man-factor-name-descends-from-eliot-waste-land.