Hallucinations: definition, causes and symptoms

Perception is the process by which living things capture information from the environment in order to process and acquire knowledge about it, being able to adapt to the situations in which we live.

However, in many cases, whether or not there is a mental disorder, perceptions occur that do not correspond to reality, and can group these perceptual alterations into distortions or disappointments, primarily.

While in perceptual distortions an actual stimulus is abnormally perceived, in perceptual disappointments there is no stimulus that triggers the perceptual process. The clearest example of this latter type of alteration in perception is that of hallucinations..

Hallucinations: defining the concept

The concept we have just mentioned, hallucination, has evolved throughout history and enriched its description over the years. Hallucination can be considered as a perception that occurs in the absence of a stimulus that triggers it, Have the patient feel that this is real and that it is happening without the subject being able to control it (this characteristic being shared with obsessions, delusions and some illusions).

Although they are usually indicators of mental disorders (being a diagnostic criterion for schizophrenia and can appear in other disorders, such as during manic episodes or during depression), hallucinations can also appear in many other cases. , such as neurological disorders, substance use, epilepsy, tumors and even in non-pathological situations of strong anxiety or stress (in the form of nervous paroxysm by the object of our anxiety, for example).

An example of hallucination

Let’s look at an example below to help us understand what a hallucination is.

“A young man arrives at a psychologist’s office. There, he tells his psychologist that he came to see him because he is very afraid. At first, he hesitates to speak to the professional, but throughout the interview, he admits that the reason for his consultation is that every time he looks at himself in the mirror, he hears a voice talking to him, insulting him, saying that he won’t get anything in life and saying that he should disappear.

This example is a fictitious case in which the supposed patient perceived a stimulus that does not really exist from a specific situation (looking in the mirror). The young man really had this perception, being for him a very real phenomenon that he can neither direct nor control.. In this way, it can be considered that it has all the features mentioned above.

However, not all hallucinations are the same. There is a great variety of typologies and classifications, among which the one that refers to the sensory modality in which they appear stands out. In addition, not all appear under the same conditions, there are also multiple variations of the hallucinatory experience.

Types of hallucinations according to the sensory modality

If we classify the hallucinatory experience according to the sensory modality in which they appear, we can find several categories.

1. Visual hallucinations

First of all, you can find the visual hallucinations, Perceived by the sense of sight. In this case, the subject sees something that does not exist in reality. These stimuli can be very simple, like flickers or lights. However, more complex elements can be seen, such as characters, cartoons or vivid scenes.

It is possible that these elements are visualized with different measures from which they would be perceived like these real stimuli, denominating Lilliputian hallucinations in the case of smaller perceptions and gulliverianas in the case of seeing them enlarged. In visual hallucinations, there is also autoscopy, in which a subject sees himself from outside his body, in a manner similar to that reported by patients with near-death experiences.

Visual hallucinations are especially common in body images, trauma, and substance use, although they also appear in some mental disorders.

2. Auditory hallucinations

Regarding the auditory hallucinationsIn which the perceiver feels something unreal, it can be simple noises or elements with full meaning like human speech.

The clearest examples are second-person hallucinations, in which, as in the above-reported example, a voice speaks to the subject, third-person hallucinations in which voices are heard speaking about its own self among them or imperative hallucinations, in which the individual hears voices ordering him to do or stop doing something. Hallucinations of this sensory modality are most common in mental disorders, Especially in paranoid schizophrenia.

3. Hallucinations of taste and smell

As for the senses of taste and smell, hallucinations in these senses are rare and are often associated with the use of drugs or other substances, in addition to certain neurological disorders such as temporal lobe epilepsy, even in tumors. They also appear in schizophrenia, usually related to delusions of poisoning or persecution.

4. Haptic hallucinations

the haptic hallucinations they are those which refer to the sense of touch. This typology includes a large number of sensations, such as temperature, pain or tingling (the latter being called paresthesias, and highlighting among them a subtype called dermatozoic delirium in which you have the sensation of having small animals in the body, being a typical substance use (such as cocaine).

Apart from these, related to the senses, two other subtypes can be identified.

First of all, kinesthetic or somatic hallucinations, which cause sensations perceived in relation to own organs, are normally linked to strange delusional processes.

Second, kinesthetic or kinetic hallucinations refer to sensations of movement in the body itself that are not produced in reality, being typical of patients with Parkinson’s disease and substance use.

As already mentioned, apart from where they are perceived, it is also useful to know how they are perceived. In this sense, we find different options.

Different ways of false perception

The so-called functional hallucinations are unleashed in the presence of a stimulus which triggers another, this time hallucinatory, in the same sensory modality. This hallucination occurs, begins and ends at the same time as the stimulus which is at the origin. An example would be the perception of someone perceiving the news air whenever he hears traffic noise.

The same phenomenon occurs in the hallucination reflectsOnly this time, the unreal perception occurs in a different sensory modality. This is the case given in the example above.

the extracampal hallucination it occurs in cases where the false perception occurs outside the perceptual field of the individual. In other words, he is perceived a little beyond what he could perceive. An example is seeing someone behind a wall, without any other data that might remind you of their existence.

Another form of hallucination is the lack of awareness of something that exists, called negative hallucination. However, in this case the behavior of the patients is not influenced as if they perceive that there is nothing, so in many cases it has become doubtful that there is a real lack of perception. An example is the negative autoscopy, In which the person does not perceive himself when looking at himself in a mirror.

Finally, it is necessary to underline the existence of pseudo-hallucinations. They are perceptions with the same characteristics as hallucinations except that the subject is aware that they are unreal elements.

Why does a hallucination occur?

We were able to see some of the main types and types of hallucinations but Why are they happening?

While there is no single explanation for this, several authors have attempted to shed light on this type of phenomenon, some of the most accepted being those who consider the subject’s attributes mistakenly hallucinating their internal experiences to external factors.

An example of this is Slade and Bentall’s theory of metacognitive discrimination, according to which the hallucinatory phenomenon is based on the inability to distinguish real perception from imaginary perception. These authors consider that this capacity of distinction, created and modifiable by learning, can be due to an excess of activation due to stress, to the lack or to the excess of environmental stimulation, to a high suggestibility, to the presence of expectations will be perceived, among other options.

Another example, focusing on auditory-type hallucinations, is Hoffman’s sub-vocalization theory, Which indicates that these hallucinations are the subject’s perception of the subvocal speech itself (i.e. our inner voice) as something foreign to itself (theory which generated therapies for treat hallucinations). Auditory with some efficiency). However, Hoffman felt that this fact was not due to a lack of discrimination, but to the generation of unintentional internal discursive acts.

Thus, hallucinations are ways of ‘reading’ reality wrongly, as if there are elements that are really there even though our senses seem to indicate otherwise. However, in the case of hallucinations, our sensory organs are functioning perfectly, which changes the way our brain processes information the one above. Typically, this means that our memories are mixed up with sensory data in an abnormal way, combining previously experienced visual stimuli with what is going on around us.

For example, this is what happens when we spend a lot of time in the dark or blindfolded so that our eyes don’t register; the brain begins to invent things due to the anomaly of not receiving data through this sensory path when awake.

The brain that creates an imaginary environment

The existence of hallucinations reminds us that we are not only recording data about what is happening around us, but that our nervous system has the mechanisms to “build” scenes that tell us what is happening around us. . Some illnesses can trigger hallucinations out of control, but these are a part of our daily lives, even if we don’t realize it.

Bibliographical references:

  • American Psychiatric Association (2002). DSM-IV-TR. Diagnostic and Statistical Manual of Mental Disorders. Spanish edition. Barcelona: Masson. (Original in English from 2000).
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  • Hoffman, RE (1986) Verbal hallucinations and language production processes in schizophrenia. Behavioral and Brain Science, 9, 503-548.
  • Ochoa E. and De la Fuente ML (1990). “Psychopathology of attention, perception and consciousness”. In Medical Psychology, Psychopathology and Psychiatry, Vol. II. Inter-American Ed. McGraw-Hill. Fountain. Madrid, p. 489-506.
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  • Slade, PD. And Bentall, RP (1988). Sensory deception: scientific analysis of hallucination. Baltimore: Johns Hopkins University.

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