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- An hallucination is a perception without a stimulus.
- With true hallucinations, the individual is convinced of the reality of the experience.
- A true hallucination must be differentiated from:
- Illusion - a misinterpretation of a stimulus (e.g., a crack on the floor is misperceived as a snake)
- Pseudohallucination - occurs in inner subjective space (e.g., heard in one’s thoughts, not perceived as auditory, does not come through the ears)
- Vivid imagery – increased imagination or mental images
- Hallucinations can occur in any of the five senses (auditory, visual, olfactory, gustatory, and/or tactile).
- Auditory hallucinations are the most common.
- Hallucinations are not pathognomic for any specific psychiatric illness, including schizophrenia.
- Hypnagogic and hypnopompic hallucinations can occur in healthy people when falling asleep and awakening, respectively.