Delusions

Annotations:

• DSM IV definition = a false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof of evidence to the contrary

1. Coltheart - just because a lot of people believe something doesn't mean it is true

Annotations:

• Sims 1995 definition = a delusion is a false, unshakeable idea or belief that is out of keeping with the patients educational, cultural and social background; it is held with extraordinary conviction and subjective certainty

1. delusions reflect higher acting belief evaluation processes that are either irrational, damaged or biased

   Annotations:

   • Top down delusions: all delusions have their main basis in higher level cognitive evaluation processes having a damaged belief evaluation system is sufficient to lead to a delusion - don't need to see weird stuff.
2. two factors

   Annotations:

   • two factors of top down theories: !) sensory/perceptual factors, 2) cognitive belief/belief evaluation factors possible to ust have the belief evaluation process applied incorrectly, irrationally or in a biased way

1. delusions are lower level and more intrinsically linked to perceptual experience. higher processes are not primary factors
2. Gold 2000

   Annotations:

   • Bottom up approach. Gold 2000 - disorders of experience without recourse to mistaken inferences
3. Mundale 2009

   Annotations:

   • Mundale 2009 (bottom up) - belief evaluation is a secondary process in the formation of delusions.  errors of delusion are part of the immediate experience of the deluded individual.
4. higher levels are involved but they are not primary locus of explanation

   Annotations:

   • bottom up - the perceptual experience is so bizarre an explanation is formed before belief evaluation process has taken place

Annotations:

• mono thematic delusion - delusions restricted to a single theme/belief/idea/topic or a small number of related beliefs.

Annotations:

• Polythematic beliefs - more diffuse - delusions impact across a number of unrelated topics/beliefs. mono thematic can develop into polythematic 

1. agency/control

   Annotations:

   • delusions of agency and control: alien hand, thought insertion, external control, voices, phantom limb
2. familiarity

   Annotations:

   • Delusions of familiarity: deja vu, jamais vu, caperas, fregoli, mirrored self misidentification 
3. nihlistic

   Annotations:

   • nihlistic delusions - cotards
4. spiritual/persecution/grandoise

   Annotations:

   • spiritual/religious/paranormal delusions: sensed presence, religion, ghosts

1. Maher 1994
   1. delusional individuals suffer primarily from sensory/perceptual anomalies which they then seek to explain

      Annotations:

      • Maher - normal reasoning and cognitive processes applied to anomalous experience.  maintained like any other strong belief and explanation reduces anxiety making it resistant to change.
      1. little evidence to show deficit in reasoning
   2. anomalous experience is necessary and sufficient to account for formation of delusions
   3. Two stage model

      Annotations:

      • Mahers theory as a two stage model: 1) anomalous sensation/experience 2) explanation of experience. Accounts for widespread nature of delusions in patients and non patient groups, allows experiencer to make sense of events.  
2. criticisms of Maher
   1. delusions not necessarily associated with anomalous perception

      Annotations:

      • Bell 2006 - delusions can occur in the absence of sensory anomalies and as such may exist at the level of reasoning/attribtuion/represention.  Chapman 1988 - delusions can occur in the absence of anomalous experience
   2. Garety - reasoning processes not entirely intact
      1. Slade and Bentall 1988

         Annotations:

         • Slade and Bentall 1988 - attribtutional biases in people with delusions are not intact
      2. Bell 2008

         Annotations:

         • Bell 2008 - perceptual experiences assessed by CAPS.  Testesd non clinical, psychotic, hallucinating deluded and non hallucinating  deluded.  non hallucinating deluded people were not significantly different from non clinical or deluded hallucinators in terms of number of anomalous perceptions reported.  
         1. don't need pathological levels of anomalous perception for delusion to occur
   3. Langdon + Coltheart 2000

      Annotations:

      • Langdon and Coltheart 2000: there is an important difference between factors responsible for the presence of delusion and factors responsible for their content
      1. perceptual distortion is necessary for bizarre form of delusion in patients, but cognitive biases contribute to content (not necessary or sufficient to account for delusion)

         Annotations:

         • Cognitive biases may be important for milder delusions and the generation of magical/paranormal/superstitious thinking
   4. experiences are often insufficient to warrant a delusional explanation - why not accept a more realistic alternative?

1. Chapman 1988

   Annotations:

   • Chapman 1988 - reasoning not always reasonable.  many misperceive ambiguous stimuli, but this is not a sensory phenomena like a hallucination 
   1. cognitive slippage

      Annotations:

      • cognitive slippage - a continuum of thought disorder/reasoning biases that underlie delusional belief
2. Garety 1994

   Annotations:

   • Garety - reasoning of schizophrenics and delusion prone people differs in some respects to controls
   1. delusions are unlikely to have a single common cause

      Annotations:

      • Garety 1994 - factors that may be involved in delusions: past experience, affect, self esteem, motivation, bias in perception, bias in judgment
3. Jump to conclusion bias

   Annotations:

   • the jump to conclusion bias reflects a failure to represent info/make choices/represent or understand probabilities/generate alternatives
   1. based on an error of probabilistic reasoning or where people do not seek sufficient evidence before they jump to conclusions, a data gathering bias

      Annotations:

      • Jump to conclusion bias task: judgement of coloured beads in a jar.  delusional jump to conclusion earlier than controls - decisions based on a mean of 2.2 beads (controls 4- 5 beads).  deluded require less info on which to base an opinion. Maher - this is not evidence for faulty reasoning - mean decision average is in line with bayesian learning/probability estimates.   Garety 1999 - nearly 1/2 based decision on one draw which is below bayesian level.
      1. been replicated

         Annotations:

         • JTC bias replicated by John 1994 and in non patient patients who had elevated scores on scales of delusional beliefs (linney 1998)
   2. JTC bias and a continuum of delusional belief

      Annotations:

      • JTC bias/continuum of delusional belief - Waxman 2007 - studied people with active delusions, delusion prone people and non delusion prone people.  JTC beads task (emotionally neutral) and self referent task (positive and negative).  deluded based judgements on less evidence and were confident in their decisions despite being inaccurate. only active delusioners differed in data gathering, active and prone = more confident when info emotionally salient
4. deluded people are able to use information correctly when given it but request less info and don't need much to reach a conclusion

   Annotations:

   • JTC is not a deficit in probabilistic reasoning but an inherent data gathering bias. deluded people show greater confidence in initial and hasty decisions and change their minds quickly - resistance to change may require prolonged period of consolidation or further evidence
5. failure to generate alternatives
   1. delusioners may fail to generate realistic interpretations
      1. inhibited by JTC bias?
         1. Freeman 2004

            Annotations:

            • Freeman 2004 - overconfidence in initial beliefs means that they fail to generate alternatives. 75% do not report alternative explanations, only the delusion.  Patients who generated alternatives reported fewer anomalous experiences and less JTC bias, as well as less conviction in delusions
            1. association between belief conviction and failure to generate alternatives
            2. absence of awareness and knowledge of internal anomalous experiences contributes to the generation of externalised delusional explanations
   2. alternative explanations not adopted because...
      1. not obvious - magic
      2. reasoning biases prevent their generation
      3. content may be more confusing or more distressing
6. Tolerance for ambiguity
   1. over reliance to resort to black and white solutions
   2. Budner 1962
      1. intolerance for ambiguity increases tendency to perceive ambiguous stimuli as threatening
   3. Kienan 1998 - associated with magical thinking
   4. Houran 1998 - linked to belief in paranormal

1. Bentall 2001 - externalising bias (due to circumstances) and personalising bias (blame others) important for persecutory delusions
2. deluded make excessive external personal attributions which defend against negative beliefs about the self

1. Frith 1987

   Annotations:

   • Frith 1987 - anomalous experiences like thought insertion/alien control/hearing voices is due to failure in system which monitors ones own actions and their preceding intentions - self monitoring bias
2. Frith 1992

   Annotations:

   • Frith 1992 - certain delusions can arise due to an inability to represent the beliefs, thoughts and intentions of others - theory of mind deficit and failure to represent information