Confusing Features of Hallucinations
Date: Saturday, December 03 @ 04:56:14 IST
Topic: Psychiatry

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All are true about hallucinations, except:
1. It is independent of will of observer
2. Sensory organs are not involved
3. It is as vivid as that in true sense perception
4. Occurs in absence of a perceptual stimulus

Well, this question is a tricky one. Let us explore the possibilities by looking at each of the statements given as options. But before moving on to that, lets quickly review the basic definition of a hallucinations:

Hallucination is a false perception characterized by externalization and a continued belief that the experience is a perception of something outside the self rather than an internal thought or image - Campbell's Psychiatric Dictionary, Eight edition.

It is independent of the will of observer - True statement
While differentiating between true perceptions and mental images, Jaspers mentioned six elements of a true perception. They are (ref: Fish's Psychopathology):
1. They are substantial (leibhaftig).
2. They appear in objective space.
3. They are clearly delineated.
4. They are constant.
5. They are independent of will.
6. Their sensory elements are full and fresh.

For a perception to qualify as a hallucination, it has to have all these six elements of true perception. Perceptual experiences lacking in one or more elements will qualify as a "pseudohallucination" (which I will discuss later).

Also, Oxford Handbook of Psychiatry, 2005 Edition defines hallucination as : A true hallucination will be perceived as being in external space, distinct from imagined images, outside conscious control, and as possessing relative permanence. -

Another argument which can be considered is that hallucinations are not a disorder of the will.

On the basis of these references, I'll safely conclude that a hallucination is independent of the will of the observer. Having said that, I would say that it is possible to classify hallucinations as voluntary and involuntary (Buchez). According to him, voluntary hallucinations are possible and are seen in some painters and other artists. But this concept has been debated time and over again. One of the arguments is that such voluntary hallucinations are non-pathological.

Sensory organs are not involved - False statement
As I have already explained, usually hallucinations are a product of our brain and not of any sensory organs except functional and reflex hallucinations.

In functional hallucination, a sensory stimulus is required in the sensory organ corresponding to the modality where the hallucination is occurring i.e. hearing church bells when telephone is ringing. Here "hearing church bells" is a hallucination and "ringing of the telephone" is the stimulus in the sensory organ (ear in this case) corresponding to the modality in which hallucination is occurring. As the hallucination is precipitated by a specific function of the corresponding sensory organ, it was termed as functional hallucination.

In reflex hallucination, you need a sensory stimulus in any other sensory organ than the one which corresponds to the modality of the hallucination. An example would be - seeing devil when telephone rings. As you can see, this hallucination is in a different modality (visual cortex) than the primary sensory organ receiving the sensory stimulus (ear). As the hallucination is occurring as a reflex to the original stimulus from a different sensory organ, it was termed as reflex hallucination.

Now this leaves us with a dilemma. What could be the right answer? Well, if we look at the question stem again, the question appears to be about all hallucinations. As functional and reflex hallucinations are also types of hallucinations, I would include them while thinking of an answer of this question. Some people might argue that they are "special" type of hallucinations and are quite rare, so it is incorrect on my part to generalize them in context of this simple question. But still I would be inclined to include them in context of this question as I feel the examiner is also testing our knowledge about subtypes of hallucinations through this seemingly innocuous question.

Before looking further, there is another concept that might also give us a reason to believe that this statement in option 2 is incorrect. According to "visual perception theory", a pathology in the sensory organs themselves can give rise to hallucination. And there is evidence to support this theory. In "Charles Bonnet Syndrome", hallucinations are known to arise secondary to blindness, an ocular pathology. Same is true with "musical auditory hallucinations" seen in deaf people. So, now we have another argument in favour of the involvement of the sensory organs in hallucinations.

Including these will obviously make the statement in option 2 an incorrect one. And as the question is about finding a single incorrect statement out of the four, this will be the correct answer!

It is as vivid as that in true sense perception - True statement
To the person having the hallucination, it is exactly the same as having a real sensory experience. Because of this objective perception by the subject, hallucinations are always percieved to be a stimulus arising in external space and appear being perceived through the sensory organs. Few people might argue that not all hallucinations are vivid, as it happened in the discussion thread on this question. To resolve this argument, I would like to point out the semantics of the statement in option 3. The statement "A hallucination is as vivid as that in true sense perception" is not defining a hallucination itself to be vivid, but is comparing the quality of the hallucination with that of a "true sense perception". We know that any hallucinatory experience, which does not match the "realistic quality" of real perception, can leave the subject confused about the origin of the stimulus. Mostly, such experiences are then perceived as arising from the "inner perceptual space". To explain this phenomenon, a term "pseudohallucination" was introduced. Although, the modern literature debates about the acceptance of the term "pseudo-hallucination", all classic and well recognized textbooks mention it. Since any "hallucination", by definition, should be perceived as "arising in the external objective space" and should have the same quality like that of a real perception, this statement is most probably true. As it is a "negatively" worded question, we will rule it out as the correct answer.

Occurs in absence of a perceptual stimulus - True statement
A hallucination is defined as a "percept without an object"(Esquirol). Going by the argument of functional and reflex hallucinations, you might say that this statement is also incorrect. Here we will have to again fall back on Jaspers' theories. According to him, the hallucinations occur at the same time as real perceptions (Ref: Fish's Psychopathology). Although in functional or reflex hallucinations, a real stimulus is responsible for starting the false perception, this real stimulus is not the cause for the hallucinatory experience, they are mere associations. A hallucination always occurs in absence of a perceptual stimulus and that is the core definition of the concept of hallucinations.

Well, I suppose I presented my arguments regarding all the options in a very open manner and try to back them up with substantial evidence. If any one differs in their opinion, they are welcome to leave their arguments in the discussion thread for this question.

P.S: During my research for finding an answer for this question, I came across a specialist out-patient psychiatry reference book by Harinder S. Ghuman. I strongly suspect that this book was the source for this question as on page 66 he defines three features of hallucinations, which cover three option statements in only slightly different wording. The only statement missing was that of "sensory organs" which we have proved incorrect.

the discussion thread for this question is located at

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