Reality monitoring ability might then be assessed by asking the participant to remember whether the second word of the word-pair had previously been perceived or imagined.
#Hallucination experiment series#
For example, a reality monitoring task might present participants with a series of verbal word-pairs (e.g., bubble and squeak), which are shown either completed (‘perceived’, that is externally generated, e.g., bubble and squeak) or where the second word must be supplied by the participant (‘imagined’, that is, internally generated, e.g., bubble and s_). Each of these variants are commonly tested using a source memory paradigm, requiring the participant to encode stimuli from different sources, and on later re-presentation of the stimuli, to judge the original source of the stimuli. Reality monitoring, involving discrimination between internal and external sources of information, such as whether a sentence had been spoken by the individual or by someone else, or even whether an event had been witnessed or dreamt. Internal source monitoring, where a distinction must be made between self-generated sources of information, such as whether a sentence had previously been spoken aloud or internally using inner speech and 3.
External source monitoring, where the distinction is between non-self-generated sources of information, such as whether an image appeared on the left or right side of a screen 2. Source monitoring can be broadly divided into three sub-categories depending on the contrasts which must be made: 1.
The Source Monitoring Framework addresses how we make judgements about the origin (source) of remembered information, using characteristics such as perceptual, semantic, or affective content, or the nature of the earlier cognitive operations ( Johnson, Hashtroudi, & Lindsay, 1993). As such, research has focused on the question of how we typically distinguish between different sources of information, and how these processes might fail. One of the most prominent cognitive models of AVH holds that these symptoms occur when internal mental events, such as inner speech, are misattributed to an external, non-self-generated source ( Bentall, 1990, Frith, 1992, Moseley et al., 2013). Cognitive and neuroscientific studies aimed at understanding the underlying mechanisms of AVH have compared task performance and/or neural activation between individuals with psychiatric diagnoses who hallucinate and those who do not ( Stephane, Kuskowski, McClannahan, Surerus, & Nelson, 2010), as well as between groups of individuals with no clinical diagnoses who report differing levels of hallucination-proneness ( Larøi, Van der Linden, & Marczewski, 2004). The significance of these findings is reviewed in light of the clinical evidence and the implications for models of hallucination generation discussed.Īuditory verbal hallucinations (AVH), or the experience of hearing a voice in the absence of any speaker, are experienced by a large proportion of individuals with a diagnosis of schizophrenia, as well as those with other psychiatric diagnoses such as bipolar disorder and post-traumatic stress disorder (PTSD), and by approximately 1% of the healthy population ( Kråkvik et al., 2015). Two experiments are presented here: the first ( N = 47, with participants selected for hallucination-proneness from a larger sample of 677 adults) found no evidence of an impairment or externalizing bias on a reality monitoring task in hallucination-prone individuals the second ( N = 124) found no evidence of atypical performance on an internal source monitoring task in hallucination-prone individuals. Much interest has focused recently on continuum models of psychosis which argue that hallucination-proneness is distributed in clinical and non-clinical groups, but few studies have directly investigated reality monitoring and internal source monitoring abilities in healthy individuals with a proneness to hallucinations. While this may be explained at least in part by an increased externalizing bias, it remains unclear whether this impairment is specific to reality monitoring, or whether it also reflects a general deficit in the monitoring of self-generated information (internal source monitoring). People with schizophrenia who hallucinate show impairments in reality monitoring (the ability to distinguish internally generated information from information obtained from external sources) compared to non-hallucinating patients and healthy individuals.
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