Zusammenfassung der Ressource
Delusions
- Definitions
- DSM IV
Anmerkungen:
- 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
- Coltheart - just
because a lot of
people believe
something
doesn't mean it
is true
- Sims 1995
Anmerkungen:
- 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
- a belief that is firmly held on
inadequate grounds and is
resistant to rational
argument or evidence to the
contrary
- approaches
- top down
- delusions reflect higher
acting belief evaluation
processes that are either
irrational, damaged or
biased
Anmerkungen:
- 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.
- two factors
Anmerkungen:
- 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
- bottom up
- delusions are lower level and more
intrinsically linked to perceptual
experience. higher processes are
not primary factors
- Gold 2000
Anmerkungen:
- Bottom up approach.
Gold 2000 - disorders of experience without recourse to mistaken inferences
- Mundale 2009
Anmerkungen:
- 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.
- higher levels
are involved but
they are not
primary locus of
explanation
Anmerkungen:
- bottom up - the perceptual experience is so bizarre an explanation is formed before belief evaluation process has taken place
- Types
- monothematic
Anmerkungen:
- mono thematic delusion - delusions restricted to a single theme/belief/idea/topic or a small number of related beliefs.
- polythematic
Anmerkungen:
- Polythematic beliefs - more diffuse - delusions impact across a number of unrelated topics/beliefs. mono thematic can develop into polythematic
- typical themes
- agency/control
Anmerkungen:
- delusions of agency and control: alien hand, thought insertion, external control, voices, phantom limb
- familiarity
Anmerkungen:
- Delusions of familiarity: deja vu, jamais vu, caperas, fregoli, mirrored self misidentification
- nihlistic
Anmerkungen:
- nihlistic delusions - cotards
- spiritual/persecution/grandoise
Anmerkungen:
- spiritual/religious/paranormal delusions: sensed presence, religion, ghosts
- Theories
- delusions as explanation
- Maher 1994
- delusional individuals
suffer primarily from
sensory/perceptual
anomalies which they
then seek to explain
Anmerkungen:
- 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.
- little evidence
to show deficit
in reasoning
- anomalous experience is
necessary and sufficient to
account for formation of delusions
- Two stage model
Anmerkungen:
- 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.
- criticisms of Maher
- delusions not
necessarily associated
with anomalous
perception
Anmerkungen:
- 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
- Garety - reasoning
processes not entirely
intact
- Slade and Bentall 1988
Anmerkungen:
- Slade and Bentall 1988 - attribtutional biases in people with delusions are not intact
- Bell 2008
Anmerkungen:
- 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.
- don't need
pathological levels
of anomalous
perception for
delusion to occur
- Langdon + Coltheart 2000
Anmerkungen:
- Langdon and Coltheart 2000: there is an important difference between factors responsible for the presence of delusion and factors responsible for their content
- 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)
Anmerkungen:
- Cognitive biases may be important for milder delusions and the generation of magical/paranormal/superstitious thinking
- experiences are
often insufficient to
warrant a delusional
explanation - why not
accept a more
realistic alternative?
- delusion as bias in reasoning
- Chapman 1988
Anmerkungen:
- Chapman 1988 - reasoning not always reasonable. many misperceive ambiguous stimuli, but this is not a sensory phenomena like a hallucination
- cognitive slippage
Anmerkungen:
- cognitive slippage - a continuum of thought disorder/reasoning biases that underlie delusional belief
- Garety 1994
Anmerkungen:
- Garety - reasoning of schizophrenics and delusion prone people differs in some respects to controls
- delusions are unlikely to have a single common cause
Anmerkungen:
- Garety 1994 - factors that may be involved in delusions: past experience, affect, self esteem, motivation, bias in perception, bias in judgment
- Jump to conclusion bias
Anmerkungen:
- the jump to conclusion bias reflects a failure to represent info/make choices/represent or understand probabilities/generate alternatives
- based on an error of
probabilistic reasoning or
where people do not seek
sufficient evidence before
they jump to conclusions, a
data gathering bias
Anmerkungen:
- 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.
- been replicated
Anmerkungen:
- JTC bias replicated by John 1994 and in non patient patients who had elevated scores on scales of delusional beliefs (linney 1998)
- JTC bias and a continuum of delusional belief
Anmerkungen:
- 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
- deluded people are able to
use information correctly when
given it but request less info
and don't need much to reach
a conclusion
Anmerkungen:
- 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
- failure to generate alternatives
- delusioners may fail to
generate realistic
interpretations
- inhibited by JTC bias?
- Freeman 2004
Anmerkungen:
- 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
- association between
belief conviction and
failure to generate
alternatives
- absence of awareness and knowledge of internal
anomalous experiences contributes to the
generation of externalised delusional explanations
- alternative explanations
not adopted because...
- not obvious -
magic
- reasoning biases
prevent their
generation
- content may
be more
confusing or
more
distressing
- Tolerance for ambiguity
- over reliance to resort to
black and white solutions
- Budner 1962
- intolerance for ambiguity
increases tendency to
perceive ambiguous stimuli
as threatening
- Kienan 1998 - associated with magical
thinking
- Houran 1998 - linked to belief in paranormal
- attributional bias - hallucinations
- Bentall 2001 - externalising bias (due
to circumstances) and personalising
bias (blame others) important for
persecutory delusions
- deluded make excessive external
personal attributions which defend against
negative beliefs about the self
- delusions as deficits in meta representation
- Frith 1987
Anmerkungen:
- 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
- Frith 1992
Anmerkungen:
- 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