Hallucinations and Perceptions

Dr Griffith
November 2008

A hallucination is defined as a sensory experience that is not based in external reality. Some hallucinations are more common than others. In bereavement or grieving, for example, it is not unusual for people to believe they have seen the deceased appear in some form, such as in a dream or far less privately, as in the case of seeing the person one is grieving, walking on the street. This experience is quite real for many people and may even be central in the processing the loss. Other hallucinations are more rare. For example, some people with Lyme disease have reported to have experienced musical hallucinations. They may hear Beethoven or Mozart as if they are at a concert hall.

In the two above examples, neither person would be diagnosed as primarily psychotic in the usual sense of that word. In the case of bereavement, the hallucination would be part of the process of working through a significant loss, whereas in the Lyme disease example, the hallucination is probably part of a neurological feature.

Hallucinations are not limited to the senses of hearing or vision. They may involve smell or touch. For example, one person suffering from psychotic depression related that she smelled burning flesh, which subsequently led to a loss of appetite and a considerable weight loss. Another person sensed something was wrong with his skin, in that he felt bugs had nested under his skin and he had the sense they were crawling toward vital organs. While the first person's smell or olfactory hallucination involved her history of war related trauma, the second person was diagnosed with paranoid schizophrenia. Some people have had skin related sensations that felt like bugs crawling on or under their skin which have been found to be related to side effects from medications. 

Sleep and Dreams 

There are other reasons people experience hallucinations. By definition, a hallucination is an altered state of consciousness. In two sleep related experiences, referred to as hypnogogic (as you're falling asleep) and hypnopompic (as you're waking up) hallucinations may occur and be quite frightening to the person experiencing them. A part of the reason for the fright is likely the timing of these hallucinations. In rapid eye movement sleep, your muscles are "paralyzed." This is the stage of sleep in which people dream, a type of hallucination itself. Though it is not clearly understood, sometimes a person can be partially awake (as in staring to fall asleep or starting to wake up) and still be in the throws of REM sleep, with all the joys of sleep paralysis! It has been reported in the medical literature that this is one way of explaining the experience of people who believe they have been visited by aliens: this experience is a type of sleep related hallucination. 
As mentioned, dreams are a type of hallucination. In the 1950s, the late Zygmunt Piotrowski developed a system he called Perceptanalysis to help understand the Rorschach Inkblot Method and he developed a method for using the Thematic Apperception Test at that time as well. In his later life, he wrote a book about his developed system of dream interpretation, based on his method of TAT analysis. He actually developed a means of assessing a person's dream responses! He felt that dreams could be evaluated empirically and like fingerprints and were unique indicators of the person's psychology.

Piotrowski believes that the "latent" or hidden aspects of dreams have been overrated. Another Sigmund, Sigmund Freud, felt dreams were often disguised, to protect the dreamer. I've often wondered whether or not Freud's theory was connected to the doctor-patient model during Victorian times. In other words, understanding dreams required professional guidance.

(However, Freud's main accomplishment, in my opinion, far overshadows any other work, that might be controversial. He pointed out that psychologically, normality is mostly an illusion and that everyone's mental health is psychodynamic, that is, fluid and variable.)

Piotrowski's difference from Freud is discussed in his book, Dreams: A Key to Self Knowledge. While it is beyond the scope of this brief note to describe these differences in detail, Piotrowski indicates that system involves

...the advanced formulation and systemization of the process of unraveling the meanings of manifest dreams; the basic PDS postulate that dreams be assessed as if they were empirical facts observed consciously in waking life. The visuomotor language of sleep dreams, however, must be first translated properly into the standardized public, verbal language.
— Piotrowski and Biele (1986)

I highly recommend his book to those wishing to explore their dreams in careful, but accessible manner.


What about daydreams? Scientists have found that daydreaming is an active process. Referred to as mind wandering, research has shown that most people, when daydreaming, are thinking about what they have to do. Also, there may be a function to daydreaming that helps a person connect the past, the present and the future. There is general certainty in the science community that the bran is not "off" when daydreaming occurs. Children daydream more frequently than adults. I do not know of any specific research that indicates the reason for this, but there do seem to be cultural prohibitions against daydreaming as an adult, as in "idle hands are the devil's work." I suspect this may be based on a kind of anti-sexual fantasy bias, that is, there may have been a belief that one's "passive" daydreaming thoughts may lead to a kind of preoccupation with sexual themes or masturbation. However, research on daydreaming indicates that the content of daydreams is rarely related any sort of sexual theme. The stuff of daydreams is generally related to more practical, day to day task oriented issues.


Many years ago, I trained, then practiced, hypnosis as part of my clinical counseling. I do not see as many practitioners of hypnosis than I did twenty years ago, though there continue to be national organized bodies of mental health clinicians, such as the American Society of Clinical Hypnosis.

The technique of hypnosis leads to a trance state and the person being hypnotized is relaxed and focused on the voice of the therapist's and his or her guidance. Usually, the therapy involves some sort of guided imagery while the person is relaxed and helps that person explore a therapeutic issue or achieve some sort of goal. It is also possible that in a trance state, that a person can hallucinate.

During a therapy session in which hypnosis was used, a client once began to hear, rather loudly, music playing. The music playing was identified clearly and was at first, a relative benign experience. Unknown to myself, the music eventually was associated with a very traumatic event in this person's life. After the person was brought back into a normal state of alertness and wakefulness, she was able to recall events that had created a rather extreme sadness and loss for her. This loss had been unresolved. The music playing was identified with a close relative's funeral and the music was the traditional military "taps." This created auditory hallucination had therapeutic stimulus value and for the next few visits, she was able to recall and experience emotions that were quite apparently never dealt with, when she suffered this loss at the age of 9.

Another form of hypnosis, which involves an alerted state is "highway hypnosis." This form of naturally induced hypnosis involves a kind of disassociation from "real time" driving. People often will often wonder where they have been, once they are reoriented. Drivers sometimes report seeing things that are not there, particularly during longer driving periods. In the descriptions I have heard, this experience highlights the distinction of illusion from hallucination.

William James (1892/1963) indicated that perception is consciousness of particular material things present to sense." (James, 1890). He has an interesting discussing of illusions and refers to illusions as false perceptions, but notes that all perception is based on the same processes, illusory or not.

Thus, illusion is essentially a kind of perceptual distortion of something in the environment. For example, a driver may see a person moving in the distance and it turns out to be a small tree blowing in the meridian. A hallucination would be the visual experience of a person walking in the meridian without the distortion of any actual object. Illusions are probably fairly common. People sometimes report hallucinations, when, in fact, they have experienced an illusion.

Change Blindness

It has been reported that the Columbus' ships were not seen by the natives as the ships approached, even though the natives were looking out onto the sea. There may be at least some truth to this.

Social psychology has done experiments involving the concept of change blindness. Change blindness does not actually represent a hallucination in the strict sense of the word, but does involve not seeing something (at least in the sense of not recognizing it) that is actually present, a kind of reverse hallucination! In one experiment (which can be seen on YouTube), a person walks up to a counter and is asked to sign a consent form. The person signs the form. The person behind the counter, ducks down and another person stands up. Research of this kind suggests about three quarters of the subjects do not see that the original person has been replaced, thus, the phenomenon is known as change blindness.

The brain has to be selective in its attention process. Otherwise, we would be overwhelmed by mountains of incoming information. Change blindness may represent a form of selective attention in which a great deal of information is missed and not initially encoded into our brain. And whether or not this was the primary reason for the Native American's allegedly inability to see the ships of Columbus is unclear.

James, William (1892/1963) Psychology.
Fawcet Publications: New York, New York

Piotrowski, Z and Biele, A (1986) Dreams: A Key to Self Knowledge.
Lawrence Erlbaum: Hillsdale, New Jersey

ArticleAustin Griffith