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Title: Is a group of individuals reporting psychotic-like experiences less susceptible to visual illusions than a non-clinical group?
Author: Drake, Emily
ISNI:       0000 0004 5994 0507
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2016
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Clin.Psy.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available