Eriko Sugimori’s talk entitled ‘Effects of Positive and Negative Delusional Ideation on Memory’ covered a study where participants were given a learning task in which they were shown 40 adjectives projected one at a time on a screen. Fifteen minutes later they were shown 80 adjectives and asked to state whether those adjectives had featured in the learning task. The participants were assessed for delusion proneness as well as degree of positive delusional ideation (consisting of traits such as guardedness, self-conceit, sense of specialness, and manipulativeness towards others) and negative delusional ideation (consisting of traits such as alienation, belittlement, persecution, and harming of others). Participants with high delusional ideation were more likely to indicate that they had learned adjectives that they had not actually learned.
In a second experiment, two forced-choice tests were conducted immediately after the learning phase. Pairs of words with similar meanings one with a positive and one with a negative connotation (eg: careful-skeptical, adventurous-reckless etc.) were presented. At the initial test phase, when presented with a forced-choice, participants were all relatively accurate in their recall (regardless of score for delusion-proneness). As time passed (when tested daily over several days) the proportion of false alarms increased among those with high proneness to delusional ideation and was correlated with their delusional style (ie those with positive traits had more false alarms with regard to positive adjectives and those with negative traits had more false alarms with regard to negative adjectives).
Kengo Miyazono’s ‘Hybrid Theory of Delusion Formation’ argues that the two-factor theory of delusion formation can be integrated with the account of delusion formation in which the notion of prediction-error plays the central role. In prediction-error theory delusions are formed in response to aberrant prediction-error signals (signals that indicate a mismatch between expectation and actual experience). In the two-factor account delusions are formed as a result of two distinct factors, these are: 1) the formation of a delusional idea and 2) the maintenance of (or inability to reject) that idea. Miyazono argues that a mis-match between expectations and actual experience could account for how a delusional idea arises due to its affect on attention allocation. Alternatively, prediction-error problems might account for the maintenance of a delusion by making belief updating excessively revisionist. In either case, on his account, prediction-error theory and two-factor accounts of delusion need not be incompatible.
Rochelle Cox’s talk gave us some results from her experiments on modelling delusions of misidentification using hypnosis and examining techniques that encourage belief revision. In her research she uses hypnosis to cause people to have temporary, reversible pathological ‘symptoms’ (such as delusions of misidentification) to provide an opportunity to examine belief maintenance and revision in the laboratory. Her research involves mistaken beliefs about the identity of oneself, other people, places, or objects and aims to identify techniques to encourage subjects to abandon their suggested beliefs. Results indicate that the most successful techniques involve active reality testing or providing subjects with an alternative explanation for their anomalous experiences. The advantages and disadvantages of these hypnotic models were discussed alongside the clinical implications of the findings.
Philip Gerrans gave a talk entitled ‘The Default Mode Network and the Cognitive Architecture of Belief Fixation. A New Approach to the One Stage -Two Stage Debate about Delusion Formation.’ Gerrans argues that delusions occur as a result of the specialized circuitry that constructs the raw material for subjective narrative interpretations of experience: The Default Mode Network (DMN) responding to anomalous or highly salient experiences. He argues that this interpretation makes sense of the phenomenology of delusions and of the neural evidence about the way the DMN and right dorsolateral-prefrontal cortex interact in psychiatric conditions. He further argues that this approach replaces debates about the rationality or irrationality of delusional beliefs with a new debate around the nature of the cognitive aetiology of delusion.
In my talk entitled ‘Delusion: A Philosophical Conceptualisation from Original Empirical Work’ I argue that some delusions should not be thought of in terms of the standard clinical definition where the focus is on false beliefs held with conviction. Whilst we might come to understand that someone is ill based on her reporting apparent beliefs held with conviction in the face of counter evidence, in some cases the pathology lies in her direct perceptual experience. Interviews with people who have clinically significant delusions highlights the bizarre and persistent nature of these anomalous perceptual experiences. I argue (along with other one-factor theorists) that in these cases no cognitive or reasoning deficit is required for these kinds of delusions to arise. We ordinarily prioritise direct experience over other information, people with these kinds of experience find them impossible to ignore and, as they persist and intensify, the experience demands an explanation.