Source monitoring for actions in hallucination proneness

In the present study we explored the role of cognitive factors in hallucinatory proneness by utilising an incidental source monitoring task consisting of actions.

A total of 65 normal subjects were administered a source monitoring task and were asked either to: (1) perform the action; (2) watch the experimenter perform the action; (3) imagine him/herself performing the action; (4) imagine the experimenter performing the action; (5) or listen to the experimenter say the action verbally. Following a delay, actions were presented consisting of those already presented in one of the 5 conditions (old), and those never before presented (new). For each action, subjects were required to identify if the action was old or new. If the action was identified as old, subjects were required to identify the source of the word (i.e., one of the 5 conditions). Subjects also completed a questionnaire assessing metacognitive beliefs. Subjects were grouped according to their scores on a revised and elaborated version of the Launay-Slade Hallucinations Scale (LSHS). Those with scores within the top 25% were included in the hallucination-prone group (HP) (n = 16), whereas scores within the lower 25% were included in the nonhallucination-prone group (NHP) (n = 16).

Within the internal conditions, hallucination-prone subjects confused two internal sources (a specific internal-internal source discrimination error). That is, for imagined actions where the subjects performed the action, HP subjects erroneously attributed these towards an imagined action performed by the experimenter. Results also revealed that hallucination-proneness was associated with metacognitive beliefs. Finally, there was a significant relation between certain metacognitive beliefs and the internal-internal source discrimination error on the source monitoring task.

Findings from the present study suggest that an important cognitive deficit in the genesis of hallucinations may be a perturbation in the control of internally generated cognitive events.