The University of Adelaide
New research from the University of Adelaide has delved into the
reasons why some people are unable to break free of their delusions,
despite overwhelming evidence explaining the delusion isn't real.
In a new paper published in the journal
Frontiers in Psychology,
University of Adelaide philosopher Professor Philip Gerrans says dreams
and delusions have a common link – they are associated with faulty
"reality testing" in the brain's higher order cognitive systems.
"Normally this 'reality testing' in the brain monitors a 'story
telling' system which generates a narrative of people's experience,"
Professor Gerrans says.
"A simple example of normal reality testing is the person who gets a
headache, immediately thinks they might have a brain tumour, then
dismisses that thought and moves on. Their story episode 'I might have
brain cancer' gets tested and quickly rejected.
"In someone who has problems with reality testing, that story might
persist and may even be elaborated and translated into action. Such
people can experience immense mental health difficulties, even to the
point of becoming a threat to themselves or to others," he says.
In his paper, Professor Gerrans discusses delusions triggered by
feelings of familiarity and unfamiliarity, such as the "Capgras
delusion" – the delusion of "doubles". One example is of a man who,
after serious head injury following a motor vehicle accident, returned
home from the hospital after a year only to state repeatedly that his
family had been replaced by impostors.
"His family looked familiar but didn’t feel familiar, and the story
in his head made sense of that feeling. It didn't matter how much
people tried to point out that his family was the same, in his mind they
had been completely replaced by impostors," Professor Gerrans says.
He says in the "Fregoli delusion", people think they're being
followed by a familiar person in disguise as a way of coping with a
feeling of familiarity evoked by seeing a stranger.
"People also experience feelings of familiarity and unfamiliarity in
déjà vu – a sense that a new place is strangely familiar, and the
reverse, jamais vu – a sense of extreme unfamiliarity evoked by a
familiar place. However, such feelings do not lead to delusion in
people whose reality testing is intact."
Professor Gerrans says better understanding this reality testing
system could help to improve outcomes for people living with such
difficulties.
"Trying to treat someone experiencing these delusions by telling them
the truth is not necessarily going to help, so new strategies need to
be developed to assist them. Ultimately, that's the aim of this work –
to help explain the nature of reality testing in order to help people
find a way of working through or around their delusions so that the
delusions no longer adversely affect their lives."
Professor Gerrans's new book, The Measure of Madness. Philosophy and
Cognitive Neuropsychiatry (MIT Press), will be published this year.
What's the difference between a dream, a delusion and an hallucination? Professor Gerrans explains:
Dream: The images, sensations and thoughts we
experience during sleep. In dreams we simply have experiences, we don't
have beliefs about experience because "reality testing" systems are not
active.
Delusion: An irrational belief at odds with reality maintained in the face of obvious contrary evidence and logical argument.
Hallucination: The apparent perception of an object not actually present.
Déjà vu: The feeling that you have previously
experienced a situation which is in fact unfamiliar. Caused by an
erroneous "sense of familiarity".
Jamais vu: The feeling that a familiar situation has not been experienced before. Caused by fleeting loss of the "sense of familiarity".
Reality Testing: The ability to determine whether a
thought or perception accurately represents reality. Largely absent in
dreams, compromised in delusion.
Editor's note: original news release can be found
here.