Hallucinations

Subjective sensations without corresponding objective stimuli; e.g., when without any corresponding auditory stimulus, voices are heard addre ing one. Any of the senses may be thus deluded, especially those of sight and hearing. Hallucinations are extremely common in certain forms of insanity, but are by no means confined to that condition; persons in apparently normal health are subject to them at times. Their cause is usually an abnormal condition of the central nervous system. See ILLUSIONS.