Is a group of individuals reporting psychotic-like experiences less susceptible to visual illusions than a non-clinical group?

Drake, Emily (2016) Is a group of individuals reporting psychotic-like experiences less susceptible to visual illusions than a non-clinical group? Doctoral thesis, University of East Anglia.

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Abstract

Background
A “basic cognitive disruption” leading to impairment in top-down and bottom-up processing is thought to underlie a number of anomalous experiences reported by individuals with psychosis. Visual illusion paradigms may be useful in exploring this potential disruption. The
primary aim was to explore whether a group of young people having psychotic-like experiences were less susceptible to visual illusions than a group of healthy controls. This study also examined the relationship between frequency of psychotic-like experiences and illusion susceptibility and the role of appraisals and emotions because they are considered an important mechanism underlying anomalies in perception.
Method
A quantitative cross-sectional design was used to compare visual illusion susceptibility scores from a clinical group of young people reporting psychotic-like experiences with a nonclinical comparison group from a student population. Relationships between illusion susceptibility; the frequency of psychotic-like experiences; appraisals and emotional
responses to psychotic-like experiences were explored within the clinical group only. Twenty-five clinical participants and 53 non-clinical participants completed a visual illusions task (measuring illusion susceptibility) and measures examining psychotic-like symptoms
and mental-health symptomology. The clinical group only completed measures examining frequency, appraisals and emotional responses to psychotic-like experiences.
Results
The research found the clinical group were significantly more susceptible to visual illusions than the non-clinical group. When depression, anxiety and stress scores were controlled for,no significant difference was found between the groups for illusion susceptibility.
Susceptibility scores were not related to frequency of psychotic-experiences; appraisals or emotional responses to anomalous experiences.
Discussion
The finding that a clinical group were more susceptible to visual illusions than a nonclinical group does not fit with Hemsley’s (2005) cognitive model. However, perceptual processing differences were observed between a clinical and non-clinical group. Theoretical and clinical implications for these findings are considered.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Brian Watkins
Date Deposited: 19 Oct 2016 11:42
Last Modified: 19 Oct 2016 11:42
URI: https://ueaeprints.uea.ac.uk/id/eprint/60992
DOI:

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