The Belief Formation Program

In the Belief Formation Project, we aim to develop a general model of the cognitive system which people use to generate, evaluate, and then accept or reject beliefs, and then to show how damage to this model could explain the occurrence of delusional beliefs - including both the widespread delusional systems seen in some people with schizophrenia, and also highly specific monothematic delusions such as Capgras, Cotard, Fregoli, and Mirrored Self-Misidentification delusions. Due to the broad nature of this aim, the project comprises several independent studies which each investigate particular cognitive and psychological processes that may be involved in the formation of particular delusional beliefs.

What are delusions?

Delusions are false beliefs, sometimes with bizarre content, that are held with strong conviction even in the presence of contrary evidence. For example, a person with the Capgras delusion might insist that his wife is an identical-looking impostor, despite that fact that his children and relatives insist that the woman is indeed his own wife. Delusional beliefs may vary on several dimensions, such as the level of conviction with which they are held, how often the person thinks about the belief, and the level of personal distress associated with the belief.

Why focus on delusions?

Delusions are first-rank markers of schizophrenia and primary features of related psychiatric disorders (schizoaffective disorder, delusional disorder, bipolar disorder). Delusions are therefore common, and occur, not only as primary features of psychiatric illness, but also in association with a large number of medical conditions (e.g., dementia, temporal lobe epilepsy, Huntington's disease, Parkinson's disease, multiple sclerosis and traumatic brain injury).

Not only do delusions vary in aetiology, they also vary dramatically in associated phenomenology. In psychiatric cases, delusions can be widespread and multi-thematic or they can be circumscribed and monothematic (examples of the latter include monothematic delusions in delusional disorder, delusions of misidentification, or cases where a schizophrenia patient only becomes delusional about the sources of their voices). The same holds for organic delusions: whereas delusional systems associated with temporal lobe damage can be widespread and co-occur with other psychotic symptoms, right hemisphere brain damage can sometimes cause focal monothematic delusions (e.g., the belief that a loved one has been replaced by an impostor).

The multiplicity of conditions that can cause delusions and the variable phenomenology associated with delusions are clinically important and theoretically challenging. Exploring what is common and what is different about delusions in varying medical conditions is critical to developing a comprehensive model of how the brain normally generates, evaluates, and then accepts (if credible) and rejects (if implausible) candidate beliefs.

Current research on monothematic delusions

Capgras delusion is the belief that someone emotionally close to you - typically a spouse - has been replaced by an identical-looking impostor. Cotard delusion is the belief that you are dead. Fregoli delusion is the belief that you are continually being followed by a group of people whom you cannot recognize because they are disguised. Mirrored-Self Misidentification is the belief that your own reflected image is a person who is following you around. Sufferers from these kinds of monothematic delusions are not delusional about anything else, and readily acknowledge the extreme implausibility of the belief they hold; but they nevertheless do not relinquish the belief. Bizarre though these conditions seem, they are not uncommon: for example, the most recent review of research on the Capgras delusion reviewed 570 cases. Delusions such as the Capgras delusion were until recently regarded as psychiatric conditions and given psychodynamic interpretations. However, there is increasing evidence to suggest that these conditions are neuropsychological in origin: Signer's review points out that in more than a third of the reported cases of Capgras delusion there was evidence of a brain lesion, typically of the right hemisphere.

Our work to date has focused on understanding these monothematic delusions by investigating underlying cognitive functioning. For example, we have now discovered two types of brain impairment that can lead to the Mirrored-Self Misidentification delusion (the belief that your own reflection is a person who is following you around). This delusion can occur in patients who have impaired face recognition and also in patients who have lost the ability to interact appropriately with mirrors. Currently we are investigating other monothematic delusions - particularly those involving misidentification of people, places or objects - in the same way in an attempt to understand how these delusions develop.

Current research on multi-thematic delusional systems

The most commonly experienced delusions in schizophrenia include the belief that certain people are conspiring against you, or trying to harm you (delusions of persecution), and the belief that non-specific social information is particularly relevant to you, or being directed at you (delusions of reference). Other prevalent delusions in schizophrenia include those with grandiose and/or religious themes (e.g., the belief that you are Jesus Christ), or the belief that alien forces are controlling your thoughts and actions (delusions of control).

Delusions of persecution and reference are characterized by fundamental aberrations in social cognition, such as the misperception of other people's intentions (e.g., as intending to cause personal harm) and/or the misinterpretation of neutral social information (including other people's mental states) as self-referent. The genesis of persecutory delusions, in particular, might involve an impaired ability to make appropriate inferences about what is going on in the minds of other people, which may in turn be related to more general deficits in social attention and reasoning. For example, one needs to be able to perform basic cognitive processes involved in recognizing mental states from people's facial expressions, and in appreciating the world from another person's point of view, in order to correctly interpret other people's intentions. Previous research within the centre has shown that healthy people who are prone to psychosis, and people with schizophrenia show difficulties performing simple visual tasks from another person's perspective. Clinically deluded and delusion-prone individuals also show impairments in their ability to identify basic emotions from other people's facial expressions, but in the real world people experience many other, more complex mental states (e.g., guilt, suspicion) that require an understanding of the social situation in which they are being experienced. The question of whether deluded individuals can make accurate use of contextual information from social situations to identify emotions and complex mental states is presently being addressed.

Basic deficits in semantic processing (i.e., processing of meaning) and semantic memory may also be precursors to delusions. The thinking style of people with schizophrenia is characterized by loose associations, and some researchers have focused their research on aberrant speech as a direct reflection of these abnormal thinking patterns. However, at MACCS we have chosen to study these thought patterns through a more detailed examination of delusional ideas. We propose that delusional thinking is a natural link between abnormal semantics (i.e., processing of meaning) and the psychopathology of schizophrenia. There have been a number of studies confirming that patients with prominent delusions do have basic deficits in semantic processing more so than other non-deluded schizophrenic patients. At MACCS we are continuing this research by examining the stability of semantic deficits over time, how these deficits relate to brain function and whether there are associated emotional processing problems.

Research into the reasoning style of people with persecutory delusions has revealed a tendency to make characteristic attributional biases for negative events. Attributions refer to the type of explanations that people give to make sense of their experiences. Most people display a Self-Serving attributional bias - that is, they tend to take the credit for good things that happen to them, and to abrogate responsibility for negative events. However, people with persecutory delusions display a distinctive attributional bias that is characterised by externalising and personalising explanations for negative events. In other words, they not only abrogate responsibility for negative events, but tend to blame other people for these events (compared with, say, attributions to chance or fate). What is not known, however, is whether this explanatory bias is an essential process involved in the formation of delusions, or whether it is simply a by-product of being in a deluded state?

This question is being addressed by studying attributional biases in both clinically deluded individuals, and non-clinical individuals showing a predisposition for paranoid thinking.

If a similar explanatory bias is evident in members of the general population who express mildly paranoid beliefs, then the question is raised of what makes the subjects with persecutory delusions delusional? Is it that they have the biases to a greater extent than those with "healthy" levels of paranoia, or is an extra ingredient necessary?

These questions are presently being investigated in the Belief Formation Project, in people with different medical conditions who are experiencing delusions, and healthy people in the general community.

The Belief Formation Participant Register has been established to facilitate recruitment of people wishing to take part in any of the studies within the Belief Formation Project. Members of the Participant Register are not obliged to take part in all (or any) of the studies, but they may be contacted with information about individual studies from time to time, to ask if they would be willing to take part.

• If you would like to volunteer as a research participant, please contact Robyn Langdon
• Belief Formation Participant Register (login required)
• More information on Schizophrenia can be found at the Schizophrenia Fellowship website