Reality monitoring performance and the role of visual imagery in visual hallucinations.

BACKGROUND: Auditory Hallucinations may arise from people confusing their own inner speech with external spoken speech. People with visual hallucinations (VH) may similarly confuse vivid mental imagery with external events. This paper reports two experiments exploring confusion between internal and external visual material. METHOD: Experiment 1 examined reality monitoring in people with psychosis; those with visual hallucinations (n = 16) and those without (n = 15). Experiment 2 used two non-clinical groups of people with high or low predisposition to VH (HVH, n = 26, LVH, n = 21). All participants completed the same reality monitoring task. Participants in Experiment 2 also completed measures of imagery. RESULTS: Psychosis patients with VH demonstrated biased reality monitoring, where they misremembered items that had been presented as words as having been presented as pictures. Patients without VH did not show this bias. In Experiment 2, the HVH group demonstrated the same bias in reality monitoring that psychosis patients with VH had shown. The LVH group did not show this bias. In addition, the HVH group reported more vivid imagery and particularly more negative imagery. CONCLUSIONS: Both studies found that people with visual hallucinations or prone-ness to such experiences confused their inner visual experiences with external images. Vivid imagery was also related to proneness to VH. Hence, vivid imagery and reality monitoring confusion could be contributory factors to understanding VH.

The effect of auditory verbal imagery on signal detection in hallucination-prone individuals.

Cognitive models have suggested that auditory hallucinations occur when internal mental events, such as inner speech or auditory verbal imagery (AVI), are misattributed to an external source. This has been supported by numerous studies indicating that individuals who experience hallucinations tend to perform in a biased manner on tasks that require them to distinguish self-generated from non-self-generated perceptions. However, these tasks have typically been of limited relevance to inner speech models of hallucinations, because they have not manipulated the AVI that participants used during the task. Here, a new paradigm was employed to investigate the interaction between imagery and perception, in which a healthy, non-clinical sample of participants were instructed to use AVI whilst completing an auditory signal detection task. It was hypothesized that AVI-usage would cause participants to perform in a biased manner, therefore falsely detecting more voices in bursts of noise. In Experiment 1, when cued to generate AVI, highly hallucination-prone participants showed a lower response bias than when performing a standard signal detection task, being more willing to report the presence of a voice in the noise. Participants not prone to hallucinations performed no differently between the two conditions. In Experiment 2, participants were not specifically instructed to use AVI, but retrospectively reported how often they engaged in AVI during the task. Highly hallucination-prone participants who retrospectively reported using imagery showed a lower response bias than did participants with lower proneness who also reported using AVI. Results are discussed in relation to prominent inner speech models of hallucinations.

The impact of negative affect on reality discrimination.

BACKGROUND AND OBJECTIVES: People who experience auditory hallucinations tend to show weak reality discrimination skills, so that they misattribute internal, self-generated events to an external, non-self source. We examined whether inducing negative affect in healthy young adults would increase their tendency to make external misattributions on a reality discrimination task. METHODS: Participants (N = 54) received one of three mood inductions (one positive, two negative) and then performed an auditory signal detection task to assess reality discrimination. RESULTS: Participants who received either of the two negative inductions made more false alarms, but not more hits, than participants who received the neutral induction, indicating that negative affect makes participants more likely to misattribute internal, self-generated events to an external, non-self source. LIMITATIONS: These findings are drawn from an analogue sample, and research that examines whether negative affect also impairs reality discrimination in patients who experience auditory hallucinations is required. CONCLUSIONS: These findings show that negative affect disrupts reality discrimination and suggest one way in which negative affect may lead to hallucinatory experiences.