Translated by Rumia Bose

In an earlier blog about hallucinations I explained how one can cope with an uncertain world. This is done with the help of a model of the world that you carry in your head. You use this model to predict what is coming and how to react. Your sensory inputs help to check the accuracy of these predictions. Here is an example which helps illustrate this. You hear a rustling noise in the bushes. Is it an animal? You don’t see one, but notice that the rustling correlates exactly with the leaves fluttering strongly in the breeze. This observation corrects the earlier prediction about an approaching animal.

Hallucinations

But sometimes what you see and hear can be ambiguous, leading to a struggle in your brain about what to believe: your prediction or your indistinct perceptions. If you – without consciously doing so – stick to your prediction despite clear signals from your senses that the prediction is incorrect, then you hallucinate. And once the connection between prediction and observation is lost, then hallucinations can lead a life of their own and you have a psychosis. See Hallucinations: seeing what you expect for a more detailed explanation and examples of how this works.

Delusions

People who are psychotic often have delusions as well as hallucinations. The same thing happens here as with hallucinations, namely that the predictions arising from the model of the world in your head are no longer corrected by reality. But in this case it is not about perceptions, such as what you see or hear, but about thoughts. These thoughts are explanations for what you perceive, what you have experienced, what is happening in the world around you. Based on these thoughts you make a coherent model to explain your world. The problem with this is that not everything you encounter in your life is logical, and some things even contradict each other¹See Man thinks ahead, Nature succeeds through hindsight.

Belief systems

Your internal model has to be coherent, otherwise you cannot base your predictions on it; predictions which you will need as you make your way in the world. When something is makes no sense or when you do not have enough information to make a coherent model, then you move on to believing in certain connections. Everybody does this, even the most exact scientist. This blog is written on the basis of my study of dozens of articles and books, in addition to a lot of thought which has gone into it. Yet nobody knows exactly how delusions arise in the brain. And still I have here a coherent narrative, or at least an attempt at one. To do this I fit established facts together, and check if other scientists share these ideas. Part of my model is based on what seems most logical. Like other scientists, I steer clear of fake news and fake facts. But because , when complex issues are concerned, all the details and how they fit together are never fully known, parts of my model are based on how I think things are. This implies a belief in conceived logic. I do pay attention to any facts which are not compatible with my model, in which case I try to take them into account.

Delusions in schizophrenia

This process is reversed in a person suffering from psychotic delusions. This person will -if he comes across facts or perceptions which do not conform to his model of the world- fit the facts to this model. This can take extreme forms, as shown in a documentary by the Dutch TV presenter Roland Duong about his mother. In the course of the film, she is shown refusing home help for the care of her swollen legs, because ” They steal my things. They have taken everything. I have nothing left” And Roland says that his mother has had schizophrenia as long as he can remember. ” This was expressed in the form of a deep-seated delusion of persecution in which the whole world was one big conspiracy against her. If we took a walk in the woods she would say: who are those people, what are they doing here, they are following us… this is so upsetting, can we never have a minute of peace…” His brother breaks in to say” She did always start off with: make sure we get that car’s number plates”.

Stopping delusions

Trying to correct someone’s delusion with facts or arguments turns out to be a fairly pointless exercise. It only leads to more suspicions and distrust. The facts themselves are ignored or explained on the basis of the delusional belief system, sometimes with absurd but uncorrectable arguments. At the start of a psychosis the delusions are usually limited in their extent. But as progressively more facts and perceptions are added to the belief system, this distorted model of the world becomes increasingly larger, less easy to correct, and begins to take the form of an absolute truth for the person concerned. This is why a person with delusions should be treated as early as possible with antipsychotics. The progressive inclusion of facts and perceptions in the delusional belief system is thereby curbed and the process can be reversed. With a bit of luck the delusions slowly fade.

Conspiracy theories

You don’t have to have schizophrenia to believe in conspiracies. That has been evident in these times of Corona. There are many such conspiracy theories and this phenomenon has always been with us. For instance, that the moon landing was staged. And the earth is flat. And children get autism through vaccines. You can call them delusions, because they are models of the world which are not correctable by facts or arguments. It is belief in conceived logic. In fact, we are talking here of collective delusions. The group collectively forms a model of the world in order to cope with it. This provides them with a clear explanation about how complex events are related to each other, although nothing about these accounts is true. People who have a greater need to find structure and purpose in all aspects of the world tend to believe more easily in conspiracy theories. To ply someone who believes in conspiracy theory with facts and arguments seems to help not at all.

References

Suthaharan, Praveen, Erin J. Reed, Pantelis Leptourgos, Joshua G. Kenney, Stefan Uddenberg, Christoph D. Mathys, Leib Litman, e.a. ‘Paranoia and Belief Updating during the COVID-19 Crisis’. Nature Human Behaviour 5, nr. 9 (september 2021): 1190–1202. https://doi.org/10.1038/s41562-021-01176-8.

Friedman RA (2020): Why Humans Are Vulnerable to Conspiracy Theories. Psychiatric Services DOI: 10.1176/appi.ps.202000348

Georgiou N, Delfabbro P, Balzan R (2020): COVID-19-related conspiracy beliefs and their relationship with perceived stress and pre-existing conspiracy beliefs. Pers Individ Dif 166:110201.

Haarsma J, Knolle F, Griffin JD, Taverne H, Mada M, Goodyer IM, et al. (2020): Influence of prior beliefs on perception in early psychosis: Effects of illness stage and hierarchical level of belief. Journal of Abnormal Psychology 129:581.

Schutte MJL, Linszen MMJ, Marschall TM, ffytche DH, Koops S, van Dellen E, et al. (2020): Hallucinations and other psychotic experiences across diagnoses: A comparison of phenomenological features. Psychiatry Research 292:113314.

Cole DM, Diaconescu AO, Pfeiffer UJ, Brodersen KH, Mathys CD, Julkowski D, et al. (2020): Atypical processing of uncertainty in individuals at risk for psychosis. NeuroImage: Clinical 26:102239.

Sterzer P, Adams RA, Fletcher P, Frith C, Lawrie SM, Muckli L, et al. (2018): The Predictive Coding Account of Psychosis. Biol Psychiatry 84:634–643.

Weilnhammer V, Röd L, Eckert A-L, Stuke H, Heinz A, Sterzer P (2020): Psychotic Experiences in Schizophrenia and Sensitivity to Sensory Evidence. Schizophr Bull DOI: 10.1093/schbul/sbaa003

Davies DJ, Teufel C, Fletcher PC (2018): Anomalous Perceptions and Beliefs Are Associated With Shifts Toward Different Types of Prior Knowledge in Perceptual Inference. Schizophr Bull 44:1245–1253.

Williams D (2018): Hierarchical Bayesian models of delusion. Conscious Cogn DOI: 10.1016/j.concog.2018.03.003

Corlett PR, Fletcher PC (2012): The neurobiology of schizotypy: Fronto-striatal prediction error signal correlates with delusion-like beliefs in healthy people. Neuropsychologia 50:3612–3620.