ABSTRACT
Is there a real divide between reality and imagination? Reality discrimination or reality monitoring are the processes by which we distinguish the two, based on memory, clarity, or availability, but false memories are easily created. True hallucinations are often distinguished from pseudo-hallucinations, illusions, and imagination, but there are no clear dividing lines. Hearing voices is common in schizophrenia; other variants, including visual, bodily, and other auditory hallucinations occur in epilepsy, sleep deprivation, sensory deprivation, and starvation, and with some ritual practices and drugs. Perceptual release hallucinations occur in lone explorers and climbers, and in Charles Bonnet syndrome affecting the newly blind or deaf. In visual hallucinations, the ‘form constants’ are common because of the structure of the visual system. Similar visions are now being created artificially, for example by Google’s Deep Dream Generator. Hallucinations provide a challenge to many theories of consciousness, including sensorimotor and predictive-processing accounts. Parapsychology is the study of psi phenomena, with methods ranging from simple card guessing to ‘ESP in the Ganzfeld’, remote viewing, and remote staring, but is consciousness involved in these phenomena? The chapter concludes with an investigation of other worlds conjured by children with imaginary playmates, shamans taking hallucinogenic drugs, or virtual reality technology.
