Definition The origin of the word “hallucination” contains two features: “to
dream” and “to be distraught.” It is supposedly derived from the Latin
alucinari, meaning “to wander in mind.” Ordinary people may speak of their
imagination “playing tricks with them” rather than hallucinations when they
are very preoccupied or interested in what is going on around them.
A hallucination is, quite simply, the perception of something—a noise, smell,
sight—that is not there. A hallucination involves sensing something while awake and conscious that is not actually physically present. It is sensation
without stimulus. A sensory hallucination may include hearing voices of
long-dead or mythical people, or it may be of insects crawling on or under the
skin. It may be of angels or fairies dancing in bright lights. Some
hallucinations are highly idiosyncratic, many transient, unreal and
bewildering.
It is important to make various distinctions between hallucinations, illusions
and delusions. An illusion is a real reaction to a real sensation with a
misattributed cause. Hence the fascination with artistic, or visual, illusions or,
indeed, with “illusion artists” who appear to do impossible things like saw
people in half. A delusion is about real reaction to a real sensation but which
is given an unreal, impossible, bizarre or overly significant cause.
Different types Hallucinations are known to be associated with many things,
including sleep (particularly sleep deprivation), certain drug use (the
obviously termed hallucinogens), mental illness (particularly psychosis) and
very specific neurological illnesses. Hallucinations occur often in
schizophrenic episodes and are described in psychiatric manuals as “a
running commentary on the person and two or more voices conversing with
each other.”
Auditory hallucinations “Hearing voices” is perhaps one of the most wellknown
“signs of madness.” It is particularly associated with the psychotic
disorders such as schizophrenia. People hear voices of specific or
unidentifiable people when others present cannot hear them. Some who
experience these hallucinations appear to be straining to listen for these
voices; others talk to themselves, sometimes pausing as if they are in
conversation. Occasionally they shout at people not physically present.
Hearing voices occurs less when a person is in conversation with a real
person present. People hear voices mostly when they are alone. Other forms
of auditory hallucination may involve hearing music—often very familiar
music that has powerful emotional associations. This can occur if listening to
very loud music for very long periods of time.
Visual hallucinations People have been reported as seeing animals, innate
objects and people not present. They may be “ghosts” or “angels” and some
involve quite complicated scenes or bizarre situations. Some visual
hallucinations are silent but in some, people speak, often directly to the
individual experiencing the hallucination and give them specific commands.
There are a whole range of highly specific visual illusions with appropriate
diagnostic labels. Thus dysmegalopsia is seeing objects misshapen or with
odd/unusual forms; micropsia and macropsia are seeing objects as either
much smaller or bigger than they really are. Allesthesia is perception that
changes the place where objects actually are, while palinopsia is the sensation
that an object that should be visually present has been removed from sight.
Diagnosis and management Diagnosticians go through a structured and
systematic medical history interview to try to determine the primary cause of
hallucinations. They would first inquire about the very specific nature of the
hallucinations—what were they like, when they first occurred, when they
typically occur, how long they have been present. Next they ask questions
about alcohol, drugs and other medication. They inquire about traumatic and
emotional events as well as evidence of physical concomitants of agitation,
confusion, fever, headaches and vomiting.
The clinical management starts with attempting to specify possible medical or
neurological causes or reactions to particular drugs “within the context of
culturally validated phenomena” (e.g. religious festival, music concerts, etc.).
Any serious psychiatric diagnosis should only occur after a very close
inspection of the nature of the hallucination and the “symptoms” that might
flow from them.
Explanations There are a number of psychological explanations for the
occurrence of hallucinations. Freudians saw hallucinations as projections of
unconscious wishes or wants. The idea was that the person experiences as
“real” something they felt but could not express because it was below
consciousness.
Cognitive psychologists point to problems in cognition processing,
particularly metacognition, which is concerned with the understanding of
others’ interpretation of events. That is, hallucinations are misinterpretations
