Hallucinations

In 2006 Olaf Blanke and his colleagues (Shahar Arzy et al.) described how, with a young woman being evaluated for surgical treatment of epilepsy, they could predictably induce a “shadow-person” by electrical stimulation of the left temporoparietal junction. When the woman was lying down, a mild stimulation of this area gave her the impression that someone was behind her; a stronger stimulation allowed her to define the “someone” as young but of indeterminate sex, lying down in a position identical to her own. When stimulations were repeated with her in a sitting position, embracing her knees with her arms, she sensed a man behind her, sitting in the same position and clasping her with his intangible arms. When she was given a card to read for a language learning test, the sitting “man” moved to her right side, and she understood that he had aggressive intentions (“He wants to take the card.… He doesn’t want me to read.”). There were thus elements of the “self” here — the mimicking or sharing of her postures by the shadow person — as well as elements of the “other.”⁹

That there may be some connection between body-image disturbances and hallucinatory “presences” was brought out as early as 1930 by Engerth and Hoff, as Blanke and his colleagues wrote in a 2006 paper. Engerth and Hoff described an elderly man who had become hemianopic after a stroke. He saw “silver things” in the blind half of his visual field, then automobiles coming at him from the left, and then people: “countless” people, all identical in appearance and with a clumsy gait, staggering, with the right arm outstretched — precisely the gait the patient himself had when he tried to walk and avoid colliding with people on his left.

But he also had alienation of his left side, and he felt that this side of his body was “filled with something strange.”

“Finally,” Engerth and Hoff wrote, “the host of hallucinations disappeared, and there then appeared what the patient called ‘a constant companion.’ Wherever the patient went, he saw someone walking along on his left.… At the moment when the companion appeared, the alien feeling in the left half of the body disappeared.… We would not be in error,” they concluded, “if we saw in this ‘companion’ the left half of the body which had become independent.”

It is not clear whether this “constant companion” is to be classified as a “sensed presence” or an autoscopic “double” — it has qualities of both. And perhaps some of these seemingly distinct categories of hallucination merge. Blanke and his colleagues, writing in 2003 of body-image, or “somatognosic,” disorders, observed that these may take a number of forms: illusions of a missing body part, a transformed (enlarged or shrunk) body part, a dislocated or disconnected body part, a phantom limb, a supernumerary limb, an autoscopic image of one’s own body, or a “feeling of a presence.” All of these disorders, Blanke stresses, with their hallucinations of vision, touch, and proprioception, are associated with parietal or temporal lobe damage.

J. Allan Cheyne has also investigated sensed presences, both in the relatively mild form that may occur when one is fully conscious and in the terrifying form that is often associated with sleep paralysis. He speculates that this feeling of “presence” — a universal human (and perhaps animal) sensation — may have a biological origin in “the activation of a distinct and evolutionary functional ‘sense of the other’ … deep within the temporal lobe specialized for the detection of cues for agency, especially those potentially associated with threat or safety.”

Sensed presence not only has its place in the neurological literature; it also forms a chapter in William James’s Varieties of Religious Experience. He recounts a number of case histories where the initially horrible feeling of an intrusive and threatening “presence” became a joyful and even blissful one, including that of a friend who told him:

It was about September, 1884, when I had the first experience … suddenly I FELT something come into the room and stay close to my bed. It remained only a minute or two. I did not recognize it by any ordinary sense and yet there was a horribly unpleasant “sensation” connected with it. It stirred something more at the roots of my being than any ordinary perception.… Something was present with me, and I knew its presence far more surely than I have ever known the presence of any fleshly living creature. I was as conscious of its departure as of its coming: an almost instantaneously swift going through the door, and the “horrible sensation” disappeared.…

[On a subsequent occasion], there was not a mere consciousness of something there, but fused in the central happiness of it, a startling awareness of some ineffable good. Not vague either, not like the emotional effect of some poem, or scene, or blossom, or music, but the sure knowledge of the close presence of a sort of mighty person.