should be distinguished from ILLUSIONS , in which an actual external stimulus is
misperceived or misinterpreted. The person may or may not have insight into the non-
veridical nature of the hallucination. One hallucinating person may recognize the false
sensory experience, whereas another may be convinced that the ex perience is grounded
in reality. The term hallucination  is not ordinarily applied to the false perceptions that
occur during dreaming, while falling asleep ( hypnagogic ), or upon awakening ( hypno-
pompic ). Transient hallucinatory experiences may occur without a mental disorder.
auditory A hallucination involving the perception of sound, most commonly of
voice.
geometric Visual hallucinations involving geometric shapes such as tunnels and
funnels, spirals, la ttices, or cobwebs.
gustatory A hallucination involving the percepti on of taste (usually unpleasant).
mood-congruent See MOOD -CONGRUENT  PSYCHOTIC  FEATURES .
mood-incongruent See MOOD -INCONGRUENT  PSYCHOTIC  FEATURES .
olfactory A hallucination involving the perception of odor, such as of burning rub-
ber or decaying fish.
somatic A hallucination involving the perception of physical experience localized
within the body (e.g., a feeling of electric ity). A somatic hallucination is to be dis-
tinguished from physical sensations arisin g from an as-yet-u ndiagnosed general
medical condition, from hypochondriacal preoccupation with normal physical
sensations, or from a tactile hallucination.
tactile A hallucination involving the perception  of being touched or of something
being under one’s skin. The most common tactile hallucinations are the sensation