Disbelief, delusions and hallucinations

Duration: 1 hour 16 mins

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Description:	Talk given by Prof Paul Fletcher as part of short course 32 (The Believing Brain)


Created:	2015-12-07 13:45
Collection:	Faraday Institute Lectures
Publisher:	Faraday Institute
Copyright:	Faraday Institute
Language:	eng (English)
Keywords:	Faraday; delusions; Religion; Hallucinations; Fletcher;


Abstract:	I will consider beliefs in the context of psychosis, a state of altered reality in which a sufferer experiences false perceptions (hallucinations) and unusual, often seemingly irrational beliefs (delusions). This state has often been considered incomprehensible since the beliefs and experiences can seem a long way from normal ways of perceiving and understanding the world. However, I argue that progress may be made by considering the normal computational challenges faced by the brain/mind in a complex, ambiguous and uncertain world, and by recognising the ways in which these challenges may be met. My starting point is that the brain must strive to be a model of the world and that, given its limited sensory access to this world, it must use inferential processing to shape its perceptions, remove ambiguity and separate the signal from the noise. The nature of this inferential processing is such that, even under normal circumstances, we may be very close to hallucinations and delusions. Moreover, this consideration brings into the question the normal distinction between perceptions and beliefs. I will speculate on the insights that psychosis may offer to the nature of perception and belief in general.

Abstract:

I will consider beliefs in the context of psychosis, a state of altered reality in which a sufferer experiences false perceptions (hallucinations) and unusual, often seemingly irrational beliefs (delusions). This state has often been considered incomprehensible since the beliefs and experiences can seem a long way from normal ways of perceiving and understanding the world. However, I argue that progress may be made by considering the normal computational challenges faced by the brain/mind in a complex, ambiguous and uncertain world, and by recognising the ways in which these challenges may be met.
My starting point is that the brain must strive to be a model of the world and that, given its limited sensory access to this world, it must use inferential processing to shape its perceptions, remove ambiguity and separate the signal from the noise. The nature of this inferential processing is such that, even under normal circumstances, we may be very close to hallucinations and delusions. Moreover, this consideration brings into the question the normal distinction between perceptions and beliefs.
I will speculate on the insights that psychosis may offer to the nature of perception and belief in general.

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