There are studies in which a subject has a magnetic field stimulated on the side of the brain (right side, IIRC) just above the right ear. The subject ‘feels the presence of beings around them, though the pre4sences are not visual.
There are all kinds of ways to induce paranormal experiences, including fasting, sleep-deprivation, electrical brain stimulation, and of course drugs. (The stories I could tell about weird intricate bizarre --- stuff--- when I was getting off of Ambien!)
But these things are all subject to clinical diagnosis. If they can be eliminated, one can really narrow down the field.