A sensory experience in contradiction to external stimuli. Most people have hallucinations; however, when they become a guiding factor in a person’s life it may be a sign of a mental disorder. There are two types of hallucinations. Positive hallucinations are when you experience something that is not actually present. (“I could have sworn I saw you at the party last night.”) Negative hallucinations are when you don’t experience something that is present. (“I looked at that table five times and didn’t see my keys there.”) The ability to produce hallucinations when a person is hypnotized is considered a sign of the depth of the hypnotic trance.