Reasoning biases and responses to psychotic experiences across the psychosis continuum

Student thesis: Doctoral ThesisDoctor of Philosophy


The prevalence of psychotic experiences (PEs) in the general population is significantly greater than comparable rates of clinical disorder, consistent with a continuum view of psychosis. Cognitive models of psychosis propose that response style and reasoning biases play an important role in determining the clinical consequences of PEs. Non-clinical individuals, with persistent PEs but no ‘need for care’, have been found to be less likely to endorse maladaptive response styles compared to a clinical psychosis group. Research is typically based on retrospective interviews, with the potential confound that maladaptive responses simply reflect intrinsically more distressing experiences within the clinical group. A novel way of addressing this issue is by exploring response styles across the psychosis continuum, using experimentally controlled anomalous experiences. In a second strand of research, individuals with persecutory beliefs have been found to make decisions on the basis of limited evidence in probabilistic reasoning tasks; the so-called ‘Jumping to Conclusions’ (JTC) data-gathering bias. Lack of belief flexibility (defined as the meta-cognitive capacity of reflecting on one's own beliefs, changing them in the light of reflection and evidence, and generating and considering alternatives) is commonly reported in around 50-75 percent of people with clinical delusions. To date, no study has compared clinical and non-clinical individuals with persistent PEs on these reasoning biases. Furthermore, there has been recent interest in integrating the literature on reasoning biases in psychosis with broader, dual process models of reasoning which distinguish between fast, automatic, Type 1 (‘experiential’) processes and slow, analytic, Type 2 (‘rational’) processes. Research in this area has tended to focus on self-reported rational and experiential reasoning with the limitation that certain reasoning processes may occur outside of conscious awareness. Finally, despite the clinical and theoretical relevance, there has been a relative lack of research focusing on the alternative explanations held by people with clinical paranoia and no current method of categorising content-level differences in subtypes of alternative explanations. This thesis investigated the role played by response style and reasoning in determining the clinical consequences of PEs, addressing the following research questions:
Research Question 1: Do individuals with persistent PEs, with and without a ‘need for care’, show differences in response styles following exposure to experimentally controlled anomalous experiences?
Research Question 2: How might the literature on reasoning biases in psychosis be integrated with broader concepts of ‘fast’ and ‘slow’ thinking within dualprocess models of reasoning?
Research Question 3: Do individuals with persistent PEs, with and without a ‘need for care’, show differences in reasoning biases and associated ‘fast’ and ‘slow’ thinking?
Research Question 4: What types of alternative explanations (AEs) are reported by individuals with clinical paranoia to explain the evidence for their persecutory belief?
Research Question 5: Do the reasoning biases under investigation combine to form latent ‘fast’ and ‘slow’ thinking factors, which predict paranoia severity within clinical samples?
Research Question 6: What are the implications of this investigation of response style and reasoning for cognitive therapy for psychosis?

The research questions were pursued in four cross-sectional empirical studies and one narrative review:
Empirical Study 1: Two groups with persistent PEs (clinical; n=84; non-clinical; n=92) and a control group without PEs (n=83) were compared on response styles following experimental analogues of thought interference (Cards Task, Telepath) and hearing voices (Virtual Acoustic Space Paradigm). Narrative Review: A narrative review was conducted on the recent literature on reasoning biases, delusional beliefs and psychosis. The state-of-the-art knowledge from systematic reviews and meta-analyses on the evidence for jumping to conclusions was summarised, before a fuller discussion of the empirical literature on belief flexibility as applied to delusions.
Empirical Study 2: Two groups with persistent PEs (clinical; n=74; non-clinical; n=92) and a control group without PEs (n=83) were compared on ‘Jumping to Conclusions’ (JTC) and belief flexibility. A randomly selected subset (n=104) was investigated to examine differences in use of experiential and rational reasoning when explaining PEs.
Empirical Study 3: Alternative Explanations (AE; a component of belief flexibility) were investigated in a large clinical sample with distressing persecutory beliefs (n=274). A system of categorising the AEs held by individuals to explain the evidence for their persecutory belief was developed. Reliability analysis was conducted, and categories presented descriptively with reference to conviction and associated distress. AEs (combining sub-types) and main belief were compared with respect to belief conviction and distress.
Empirical Study 4: Drawing on the same sample as Empirical Study 3, associations between presence of AEs and other reasoning biases (Possibility of being mistaken (PM) and JTC) and paranoia severity were investigated. The hypothesis that paranoia involves reduced ‘slow thinking’ and over-reliance on ‘fast thinking’ was tested using formally assessed reasoning biases and a latent variable analytic approach.

Empirical Study 1: The non-clinical group with PEs were less likely to endorse maladaptive response styles, such as attempts to avoid, suppress, worry about or control mental experiences, compared to the clinical group on all tasks. The clinical group were more likely to endorse unhelpful response styles compared to controls on two out of three tasks. The non-clinical group performed similarly to controls on maladaptive responding across all tasks. There were no group differences for adaptive response styles, such as cognitive reappraisal or mindful acceptance of experiences. Narrative review: Dual process models of reasoning, popularised as ‘fast and slow thinking’, were considered to offer a useful theoretical framework for 7 integrating research on reasoning biases in psychosis with implications for research and clinical practice.
Empirical Study 2: The JTC reasoning bias was more common in the clinical group than the other two groups. Unexpectedly, no group differences were observed between clinical and non-clinical groups with PEs on measures of belief flexibility. However, the clinical group was less likely to employ rational reasoning, while the non-clinical group was more likely to use experiential reasoning plus a combination of both types of reasoning processes, compared to the other two groups.
Empirical Study 3: 129 individuals (47%) were able to provide an AE for the evidence they have for their main persecutory belief. AEs were categorised, with excellent reliability, into eleven categories: Thirty percent of the AEs were categorised under a broad ‘Illness’ category with unelaborated mental health explanations the single most common subcategory across all AEs. As well as being the most common, this category was associated with the lowest level of conviction. Over fifty percent of the AEs fell within the broad psychological category of ‘Misinterpretation’. AEs which involved recognition that the experiences were not personal or specifically targeted (‘Misinterpretation: nonpersonalising’) were associated with the lowest distress of any sub-category, although conviction in these AEs was comparatively low. When combined across all categories, AEs were rated as less distressing but also held with lower conviction when compared to the main distressing belief.
Empirical Study 4: The presence of an AE was associated with PM and mean beads drawn on the JTC tasks. Individuals with an AE showed lower conviction and paranoia severity compared to those with no AE, across a range of assessments. The components of belief flexibility (AE and PM) formed a latent ‘Slow thinking’ factor, with higher levels of slow thinking associated with lower conviction and paranoia severity across all measures. The JTC tasks also formed a latent ‘Fast thinking’ factor which, as expected, was negatively correlated with ‘Slow thinking’. However, contrary to expectation, ‘fast thinking’ was not positively associated with paranoia conviction or severity.

The thesis addressed calls for an increased focus on the study of individuals for whom marked and persistent PEs are associated with functional outcomes. Evidence was presented of novel protective factors which include less likelihood of engaging in maladaptive responding, less tendency to jump to conclusions and a preserved ability to engage in slower analytical thinking around unusual experiences. The findings carry important implications for cognitive and continuum models of psychosis. A rigid, maladaptive response style (characterised by attempts to avoid, control or suppress experiences), may represent a ‘default mode’ for many clinical individuals and therefore an important treatment target. The empirical studies enriched our understanding of the diverse ways in which individuals across the psychosis continuum make sense of anomalous and ambiguous experiences. The system of categorising AEs provides a framework for future research into whether certain forms of AE might be stronger moderators of response to targeted treatments and/or be more likely to emerge following successful treatment. Evidence, in clinical samples, that ‘slow thinking’ was more strongly associated with paranoia severity than ‘fast thinking' suggests a valuable therapeutic focus on promoting slower, reflective thinking with the aim of facilitating engagement with helpful alternative content in daily life.
Date of Award1 Jun 2020
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorPhilippa Garety (Supervisor), Emmanuelle Peters (Supervisor) & Thomas Jamieson-Craig (Supervisor)

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