Skip to main content

Externalizing biases and hallucinations in source-monitoring, self-monitoring and signal detection studies: a meta-analytic review

  • M. L. Brookwell (a1), R. P. Bentall (a2) and F. Varese (a2) (a3)

Cognitive models have postulated that auditory hallucinations arise from the misattribution of internally generated cognitive events to external sources. Several experimental paradigms have been developed to assess this externalizing bias in clinical and non-clinical hallucination-prone samples, including source-monitoring, verbal self-monitoring and auditory signal detection tasks. This meta-analysis aims to synthesize the wealth of empirical findings from these experimental studies.


A database search was carried out for reports between January 1985 and March 2012. Additional studies were retrieved by contacting authors and screening references of eligible reports. Studies were considered eligible if they compared either (i) hallucinating and non-hallucinating patients with comparable diagnoses, or (ii) non-clinical hallucination-prone and non-prone participants using source-monitoring, verbal self-monitoring or signal detection tasks, or used correlational analyses to estimate comparable effects.


The analysis included 15 clinical (240 hallucinating patients and 249 non-hallucinating patients) and nine non-clinical studies (171 hallucination-prone and 177 non-prone participants; 57 participants in a correlation study). Moderate-to-large summary effects were observed in both the clinical and analogue samples. Robust and significant effects were observed in source-monitoring and signal detection studies, but not in self-monitoring studies, possibly due to the small numbers of eligible studies in this subgroup. The use of emotionally valenced stimuli led to effects of similar magnitude to the use of neutral stimuli.


The findings suggest that externalizing biases are important cognitive underpinnings of hallucinatory experiences. Clinical interventions targeting these biases should be explored as possible treatments for clients with distressing voices.

Corresponding author
*Address for correspondence: F. Varese, Ph.D., University of Liverpool, Liverpool, UK. (Email:
Hide All
Aleman, A, Larøi, F (2008). Hallucinations: The Science of Idiosyncratic Perception. American Psychological Association: Washington, DC.
Allen, P, Amaro, E, Fu, C, Williams, SCR, Brammer, MJ, Johns, LC, McGuire, PK (2007). Neural correlates of the misattribution of speech in schizophrenia. British Journal of Psychiatry 190, 162169.
Allen, P, Freeman, D, Johns, L, McGuire, P (2006). Misattribution of self-generated speech in relation to hallucinatory proneness and delusional ideation in healthy volunteers. Schizophrenia Research 84, 281288.
Allen, P, Johns, LC, Fu, C, Broome, MR, Vythelingum, G, McGuire, PK (2004). Misattribution of speech in patients with hallucinations and delusions. Schizophrenia Research 69, 277287.
Anselmetti, S, Cavallaro, R, Bechi, M, Angelone, SM, Ermoli, E, Cocchi, F, Smeraldi, E (2007). Psychopathological and neuropsychological correlates of source monitoring impairment in schizophrenia. Psychiatry Research 150, 5159.
Arguedas, D, Stevenson, RJ, Langdon, R (2012). Source monitoring and olfactory hallucinations in schizophrenia. Journal of Abnormal Psychology 121, 936943.
Barkus, E, Smallman, R, Royle, N, Barkus, C, Lewis, S, Rushe, T (2011). Auditory false perceptions are mediated by psychosis risk factors. Cognitive Neuropsychiatry 16, 289302.
Barkus, E, Stirling, J, Hopkins, R, McKie, S, Lewis, S (2007). Cognitive and neural processes in non-clinical auditory hallucinations. British Journal of Psychiatry Supplement 191, s76s81.
Bendall, S, Jackson, HJ, Hulbert, CA (2011). What self-generated speech is externally misattributed in psychosis? Testing three cognitive models in a first-episode sample. Scizophrenia Research 129, 3641.
Bentall, RP (1990). The illusion of reality: a review and integration of psychological research on hallucinations. Psychological Bulletin 107, 8295.
Bentall, RP (2003). Madness Explained: Psychosis and the Human Nature. Penguin Books Ltd: London.
Bentall, RP, Baker, GA, Havers, S (1991). Reality monitoring and psychotic hallucinations. British Journal of Clinical Psychology 30, 213220.
Bentall, RP, Slade, P (1985 a). Reality testing and auditory hallucinations: a signal detection analysis. British Journal of Clinical Psychology 24, 159169.
Bentall, RP, Slade, P (1985 b). Reliability of a scale measuring disposition towards hallucination: a brief report. Personality and Individual Differences 6, 527529.
Brébion, G, Amador, X, David, AS, Malaspina, D, Sharif, Z, Gorman, JM (2000). Positive symptomatology and source-monitoring failure in schizophrenia – an analysis of symptom-specific effects. Psychiatry Research 95, 119131.
Brébion, G, Ohlsen, RI, Pilowsky, LS, David, AS (2008). Visual hallucinations in schizophrenia: confusion between imagination and perception. Neuropsychology 22, 383389.
Brunelin, J, Combris, M, Poulet, E, Kallel, L, d'Amato, T, Dalery, J, Saoud, M (2006). Source monitoring deficits in hallucinating compared to non-hallucinating patients with schizophrenia. European Psychiatry 21, 259261.
Cohen, J (1988). Statistical Power Analysis for the Behavioural Sciences. Erlbaum: Hillsdale, NJ.
Ditman, T, Kuperberg, GR (2005). A source-monitoring account of auditory verbal hallucinations in patients with schizophrenia. Harvard Review of Psychiatry 13, 280299.
Duval, S, Tweedie, R (2000). Trim and fill: a simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis. Biometrics 56, 455463.
Egger, M, Davey Smith, G, Schneider, M, Minder, C (1997). Bias in meta-analysis detected by a simple, graphical test. British Medical Journal 315, 629634.
Favrod, J, Vianin, P, Pomini, V, Mast, FV (2006). A first step towards cognitive remediation of voices: a case study. Cognitive Behaviour Therapy 35, 159163.
Feinberg, I (1978). Efference copy and corollary discarge: implications for thinking and its disorders. Schizophrenia Bulletin 4, 636640.
Fisher, M, McCoy, K, Poole, JH, Vinogradov, S (2008). Self and other in schizophrenia: a cognitive neuroscience perspective. American Journal of Psychiatry 165, 14651472.
Ford, JM, Mathalon, DH (2005). Corollary discharge dysfunction in schizophrenia: can it explain auditory hallucinations? International Journal of Psychophysiology 58, 179189.
Frith, C (1992). The Cognitive Neuropsychiatry of Schizophrenia. Lawrence Erlbaum: Hove.
Frith, C, Done, DJ (1988). Towards a neuropsychology of schizophrenia. British Journal of Psychiatry 153, 437443.
Harvey, PD (1985). Reality monitoring in mania and schizophrenia: the association of thought disorder and performance. Journal of Nervous and Mental Disease 173, 6773.
Hedges, LV (1981). Distribution theory for Glass's estimator of effect size and related estimators. Journal of Educational Statistics 6, 107128.
Higgins, JPT, Thompson, SG, Deeks, JJ, Altman, DG (2003). Measuring inconsistency in meta-analyses. British Medical Journal 327, 557560.
Hoffman, RE (1986). Verbal hallucinations and language production processes in schizophrenia. Behavioral and Brain Sciences 9, 503548.
Honig, A, Romme, M, Ensink, B, Escher, S, Pennings, M, DeVries, M (1998). Auditory hallucinations: a comparison between patients and nonpatients. Journal of Nervous and Mental Disease 186, 646651.
Johns, LC, Gregg, L, Allen, P, McGuire, PK (2006). Impaired verbal self-monitoring in psychosis: effects of state, trait and diagnosis. Psychological Medicine 36, 465474.
Johns, LC, Rossell, S, Frith, C, Ahmad, F, Hemsley, D, Kuipers, E, McGuire, PK (2001). Verbal self-monitoring and auditory verbal hallucinations in patients with schizophrenia. Psychological Medicine 31, 705715.
Johnson, MK, Hashtroudi, S, Lindsay, DS (1993). Source monitoring. Psychological Bulletin 114, 328.
Keefe, RSE, Arnold, MC, Bayen, UJ, Harvey, PD (1999). Source monitoring deficits in patients with schizoprenia; a multinomial modelling analysis. Psychological Medicine 29, 903914.
Larøi, F, van der Linden, M, Marczewski, P (2004). The effects of emotional salience, cognitive effort and meta-cognitive beliefs on a reality monitoring task in hallucination-prone subjects. British Journal of Clinical Psychology 43, 221233.
Moritz, S, Woodward, TS, Ruff, CC (2003). Source monitoring and memory confidence in schizophrenia. Psychological Medicine 33, 131139.
Morrison, AP, Haddock, G (1997). Cognitive factors in source-monitoring and auditory hallucinations. Psychological Medicine 27, 669679.
Morrison, AP, Renton, JP, Dunn, H, Williams, S, Bentall, RP (2003). Cognitive Therapy for Psychosis: A Formulation-Based Approach. Routledge: Hove.
Perona-Garcelán, S, Carrascoso-López, F, García-Montes, JM, Vallina-Fernández, O, Pérez-Álvarez, M, Ductor-Recuerda, MJ, Salas-Azcona, R, Cuevas-Yust, C, Gómez-Gómez, MT (2011). Depersonalization as a mediator in the relationship between self-focused attention and auditory hallucinations. Journal of Trauma and Dissociation 12, 535548.
Rankin, PM, O'Carroll, PJ (1995). Reality discrimination, reality monitoring and disposition towards hallucination. British Journal of Clinical Psychology 34, 517528.
Seal, ML, Crowe, SF, Cheung, P (1997). Deficits in source monitoring in subjects with auditory hallucinations may be due to differences in verbal intelligence and verbal memory. Cognitive Neuropsychiatry 2, 273290.
Serper, M, Dill, CA, Chang, N, Kot, T, Elliot, J (2005). Factorial structure of the hallucinatory experience: continuity of experience in psychotic and normal individuals. Journal of Nervous and Mental Disease 193, 265272.
Slade, P, Bentall, RP (1988). Sensory Deception: A Scientific Analysis of Hallucination. Croom Helm: London.
Stephane, M, Kuskowski, M, McClannahan, K, Sureus, C, Nelson, K (2010). Evaluation of speech misattribution bias in schizophrenia. Psychological Medicine 40, 741748.
Subramaniam, K, Luks, TL, Fisher, M, Simpson, GV, Nagarajan, S, Vinogradov, S (2012). Computerized cognitive training restores neural activity within the reality monitoring network in schizophrenia. Neuron 73, 842853.
van Os, J, Hanssen, M, Bijl, RV, Ravelli, A (2000). Strauss (1969) revisited: a psychosis continuum in the normal population? Schizophrenia Research 45, 1120.
van Os, J, Linscott, RJ, Myin-Germeys, I, Delespaul, P, Krabbendam, L (2009). A systematic review and meta-analysis of the psychosis continuum: evidence for a psychosis proneness–persistence–impairment model of psychotic disorder. Psychological Medicine 39, 179195.
Varese, F, Barkus, E, Bentall, RP (2011). Dissociative and metacognitive factors in hallucination-proneness when controlling for comorbid symptoms. Cognitive Neuropsychiatry 16, 193217.
Varese, F, Barkus, E, Bentall, RP (2012). Dissociation mediates the effect of childhood trauma on hallucination-proneness. Psychological Medicine 42, 10251036.
Varese, F, Bentall, RP (2011). The metacognitive beliefs account of hallucinatory experiences: a literature review and meta-analysis. Clinical Psychology Review 31, 850864.
Vercammen, A, De Haan, EHF, Aleman, A (2008). Hearing a voice in the noise: auditory hallucinations and speech perception. Psychological Medicine 38, 11771184.
Versmissen, D, Janssen, I, Johns, LC, McGuire, PK, Drukker, M, Campo, J, Myin-Germeys, I, Van Os, J, Krabbendam, L (2007). Verbal self-monitoring in psychosis: a non-replication. Psychological Medicine 37, 569576.
Waters, F, Allen, P, Aleman, A, Fernyhough, C, Woodward, TS, Badcock, JC, Barkus, E, Johns, L, Varese, F, Menon, M, Vercammen, A, Larøi, F (2012 a). Auditory hallucinations in schizophrenia and nonschizophrenia populations: a review and integrated model of cognitive mechanisms. Schizophrenia Bulletin 38, 683693.
Waters, F, Woodward, TS, Allen, P, Aleman, A, Sommer, I (2012 b). Self-recognition deficits in schizophrenia patients with auditory hallucinations: a meta-analysis of the literature. Schizophrenia Bulletin 38, 741750.
Woodward, TS, Menon, M (2011). Considerations for analysis of source monitoring data when investigating hallucinations in schizophrenia research. European Archives of Psychiatry and Clinical Neuroscience 261, 157164.
Woodward, TS, Menon, M, Whitman, JC (2007). Source monitoring biases and auditory hallucinations. Cognitive Neuropsychiatry 12, 477494.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Psychological Medicine
  • ISSN: 0033-2917
  • EISSN: 1469-8978
  • URL: /core/journals/psychological-medicine
Please enter your name
Please enter a valid email address
Who would you like to send this to? *



Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed