Impaired discrimination between imagined and performed actions in schizophrenia.

Abstract

The main aim of the present study was to investigate whether a specific type of source monitoring, namely self-monitoring for actions (differentiation between imagined and performed actions), is disrupted in schizophrenia. Persons diagnosed with schizophrenia (n=32) and healthy participants (n=32) were assessed with an action memory task. Simple actions were presented to the participants either verbally (short instructions) or nonverbally (icons). Some of the items required participants to physically perform the action whereas other actions had to be imagined. In the recognition phase of the study, participants were asked whether an action was previously displayed (verbally or nonverbally), whether it was a new action (not presented before), and if they had performed or imagined the action. In addition, participants were asked how confident they were in their decision. Participants in the group with schizophrenia significantly more often misattributed imagined actions as performed and vice versa and were more convinced about their wrong decision than participants in the control group. Patients revealed worse recognition for both verbal and nonverbal actions. In accordance with prior studies, we found that patients were less confident in their correct answers than healthy subjects. However, no enhanced confidence in incorrect answers was found. There was no observed significant relationship between source misattributions and the severity of psychopathological symptoms. Our findings suggest tentatively general source monitoring deficits in schizophrenia.

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Impaired discrimination between imagined and performed actions in schizophrenia
Łukasz Gawędaa,⁎, Steffen Moritzb, Andrzej Kokoszkaa
aII Department of Psychiatry, Medical University of Warsaw, Warsaw, Poland
bUniversity Hospital Hamburg-Eppendorf, Department for Psychiatry and Psychotherapy, Hamburg, Germany
a b s t r a c ta r t i c l ei n f o
Article history:
Received 14 November 2010
Received in revised form 20 July 2011
Accepted 23 July 2011
Keywords:
Schizophrenia
Source monitoring
Action monitoring
Self-monitoring
Action memory
Metamemory
The main aim of the present study was to investigate whether a specific type of source monitoring, namely
self-monitoring for actions (differentiation between imagined and performed actions), is disrupted in
schizophrenia. Persons diagnosed with schizophrenia (n=32) and healthy participants (n=32) were
assessed with an action memory task. Simple actions were presented to the participants either verbally (short
instructions) or nonverbally (icons). Some of the items required participants to physically perform the action
whereas other actions had to be imagined. In the recognition phase of the study, participants were asked
whether an action was previously displayed (verbally or nonverbally), whether it was a new action (not
presented before), and if they had performed or imagined the action. In addition, participants were asked how
confident they were in their decision. Participants in the group with schizophrenia significantly more often
misattributed imagined actions as performed and vice versa and were more convinced about their wrong
decision than participants in the control group. Patients revealed worse recognition for both verbal and
nonverbal actions. In accordance with prior studies, we found that patients were less confident in their correct
answers than healthy subjects. However, no enhanced confidence in incorrect answers was found. There was
no observed significant relationship between source misattributions and the severity of psychopathological
symptoms. Our findings suggest tentatively general source monitoring deficits in schizophrenia.
© 2011 Elsevier Ireland Ltd. All rights reserved.
1. Introduction
Cognitive biases are frequently observed among persons with
schizophrenia (e.g. Moritz et al., 2005; Bell et al., 2006; Moritz et al.,
2006; Freeman, 2007) and are putatively involved in the pathogenesis
of reality distortion (e.g. Bentall, 1990). Recently, an increasing
number of studies examined whether or not people diagnosed with
schizophrenia tend to confuse sources of information (e.g. Anselmetti
et al., 2007; Startup et al., 2008). This line of research is particularly
concerned with source monitoring deficits and its relationship to the
psychopathology of schizophrenia, especially the positive symptoms
of the disorder (for review see Laroi and Woodward, 2007).
Source monitoring encompasses three different judgment classes
(Johnson et al., 1993): a) reality monitoring which is the differentiation
betweeninternalandexternalsourcesofinformation;b)self-monitoring
which is the differentiation between two internal sources (e.g. imagery
and real performance); c) differentiation between different external
sources.
Most studies that have addressed source monitoring in schizophre-
nia were concerned with the differentiation of internal versus external
sources (reality monitoring). These tasks usually involve the presenta-
tion of verbal material from various sources. For example, participants
have to generate words themselves or words are provided for them by
an external source (e.g. experimenter or computer). Later, the
participant is asked to recollect the source of information. It was
foundthatpatientswithschizophreniaoftenperceivedthatwordswere
produced by theexperimenter (or other externalsources), when in fact
they were produced by the participants themselves (e.g. Vinogradov
et al., 1997; Baker and Morrison, 1998; Allen et al., 2004). Poor source
monitoring among patients with schizophrenia is now a well-
documented deficit. However, findings are rather mixed concerning
the association between source monitoring and specific symptoms of
schizophrenia.Someauthorshavefoundthatsourcemonitoringdeficits
are related to positive symptoms (Baker and Morrison, 1998; Brebion
et al., 2000, 2002; Allen et al., 2004; Brunelin et al., 2006; Johns et al.,
2006; Anselmetti et al., 2007; Startup et al., 2008), whereas others have
reported a connection with thought disorganization (Nienow and
Docherty, 2004) or negative symptoms (Brebion et al., 2002; Moritz
etal.,2003).Finally,somestudieshavefoundsourcemonitoringdeficits
in schizophrenia, but these deficits were not related to specific
symptoms of the disorder (e.g. Vinogradov et al., 1997). Recently
some authors have found (Brunelin et al., 2007) that source monitoring
deficits may represent a general vulnerability factor to schizophrenia,
rather than a state marker for a particular class of symptoms.
Interestinglyandconsistentwiththisfinding,sourcemonitoringdeficits
were found amongpsychosis-prone healthy subjects (Laroi et al., 2005;
Allen et al., 2006; Peters et al., 2007) indicating that such disturbances
are precursors rather than consequences of the disorder. Challenging
Psychiatry Research 195 (2012) 1–8
⁎ Corresponding author at: II Department of Psychiatry, Medical University of
Warsaw, ul. Kondratowicza 8, 03-242 Warsaw, Poland. Tel./fax: +48 22 326 58 92.
E-mail address: lgaweda@wum.edu.pl (Ł Gawęda).
0165-1781/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.psychres.2011.07.035
Contents lists available at ScienceDirect
Psychiatry Research
journal homepage: www.elsevier.com/locate/psychres

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these findings, Szöke et al. (2009) found source monitoring to be rather
a state-dependent factor for psychotic symptoms.
The source monitoring deficits in schizophrenia are not restricted to
one single type of misattribution. Keefe et al. (1999) found that
schizophrenia subjects fail to discriminate between internal and
external sources (reality monitoring), as well as between two external
sourcesandtwointernalsources(self-monitoring).Yet,self-monitoring
is relatively understudied in schizophrenia.Further, theself-monitoring
may be particularly interesting in psychosis pertaining to one's inability
to discriminate between reality and fantasy and hence if impaired
consequently maybeinvolved in reality distortionsthat are observed in
schizophrenia. Elevated imagery (Ortel et al., 2009), as well as an
imbalancebetweenfantasyandrealityispresentinschizophreniaandis
thus linked to the reality distortions of this group (Böcker et al., 2000).
Interestingly, it was found that elevated imagery may blur differences
between fantasies and reality, thus fostering self-monitoring errors
(Johnson et al., 1979, 1988).
Franck and coworkers (2000) examined self-monitoring in schizo-
phrenia by asking participants to read a text silently versus aloud. After
5-min delay, they were questioned about how they read the text.
Subjects with schizophrenia misattributed a text as having been read
aloud,wheninfactthetextwasreadsilently.Morerecently,Henquetet
al. (2005) obtained similar results. They report that persons with
schizophrenia misperceived imagined events as verbalized. Interest-
ingly, behavioral studies of self-monitoring in schizophrenia have been
validated by using neuroimaging. Researchers found that that distin-
guishing between imagined and perceived events engaged brain
structures that are consistently impaired in schizophrenia: the
prefrontal cortex, thalamus and cerebellum (Simons et al., 2006).
Moreover, some authors suggest that source monitoring deficits in
schizophrenia are not restricted to one particular type of performance
and may also include physical actions (Frith, 1992). However, the
majority of studies have tested source monitoring by administering
verbal material which later has to be remembered. Recently, Brodeur
et al. (2009) found that persons with schizophrenia have difficulties
memorizing the source of actions. In this study, participants had to
either enact an action, to observe an action performed by the
experimenter, or had to read about an action. Results revealed that
participants diagnosed with schizophrenia tended to falsely recollect
observed actions at the same rate as self-performed actions. Unfortu-
nately, the methodology of the study did not provide adequate
conclusions about self-monitoring.
Difficulties in the self-monitoring for actions were found in high-
schizotypal healthy subjects (Laroi et al., 2005). To date, few studies
addressed self-monitoring for actions among persons diagnosed with
schizophrenia (Mammarella et al., 2010). In accordance with studies
conducted for psychosis-prone subjects, it was found that persons
with schizophrenia misperceive imagined actions as being physically
performed (Mammarella et al., 2010). Source recognition in this study
was performed 24 h after the learning phase. Thus, apart from source
memory, the task also engages long term memory. Moreover, only
verbal stimuli were presented, and thus the influence of the way in
which the stimuli were administered (verbally vs. nonverbally) could
not be investigated. One source monitoring study conducted in
patients with obsessive-compulsive disorder found that nonverbal
action stimuli were more difficult to recognize than verbal stimuli
(Moritz et al., 2009). This finding suggests the influence of action's
presentation type on source monitoring.
To fill some of the aforementioned empirical gaps, the main aim of
the present study was to investigate whether a specific type of source
monitoring, namely self-monitoring for actions (differentiation be-
tween imagined and performed actions), is disrupted in schizophrenia.
In addition, we controlled for the type of presentation: actions were
either presented verbally (text) or nonverbally (icons). It was expected
that subjects with schizophrenia would show more self-monitoring
deficits and incorrect attributions about stimuli presentation than
healthyparticipants.Moreprecisely,wehypothesizedthatpersonswith
schizophreniawouldmorefrequentlythancontrolsubjectsmisperceive
actions that had to be imagined versus physically performed and vice
versaaswell asmisattribute verbal versus nonverbal actionsmore than
control subjects. In addition we were interested in another important
facet of cognition, namely response confidence, that along with source
monitoring may contribute to reality distortions in schizophrenia. For
example, Moritz et al. (2005) and Moritz and Woodward (2002) found
that patients with schizophrenia are more confident than healthy
subjects in incorrect memories and less confident in correct memories.
Intheir firststudy on source monitoring, Moritzetal. (2003) found that
personsdiagnosedwithschizophreniacommittedmoresourcememory
errors. Again, they were more confident in incorrect attributions and
less confident in correct ones than the control group. Furthermore, for
our study it was expected that self-monitoring errors as well as failures
in discriminating presentation type (verbal and nonverbal actions)
would be accompanied with high cognitive confidence and that correct
answers would be related to low cognitive confidence in the
schizophrenia group. Finally, we were interested as to whether self-
monitoring errors, discrimination of action's presentation type and
cognitive confidence would be related to particular schizophrenia
symptoms. However, because of the small number of subjects, this
analysis was considered as a preliminary.
2. Methods
2.1. Participants
Thirty-two inpatient and outpatient persons with diagnosis of schizophrenia or
schizoaffective disorder were recruited from the II Department of Psychiatry, Medical
University of Warsaw and from The Institute of Psychiatry and Neurology, Warsaw
(Poland). All of them were stable and taking a sufficient dosage of antipsychotics. Also,
none of the participants showed aggressive behavior or severe formal thought
disorder. Fifteen patients were deluded and nine experienced auditory hallucinations;
the remaining eight patients were in remission. Clinical diagnosis of the specialist in
psychiatry was confirmed by a structured interview with the Neuropsychiatric
Interview (MINI, Sheehan et al., 1998). Exclusion criteria for the study were as follows:
equivocal diagnosis, any current alcohol or other substance dependence, and presence
of severe neurological disorders (e.g. stroke). Thirty-two healthy participants served as
controls and were recruited by word-of-mouth and advertisement. The lack of life-time
prevalence of any mental disorders was verified by MINI interview (Sheehan et al.,
1998). Every participant took part in the study after informed consent was obtained.
The study received the approval of the local ethical committee.
2.2. Psychopathology assessment
Psychopathology in the group with schizophrenia was assessed with the widely
used Positive and Negative Syndrome Scale (PANSS, Kay et al., 1986) following a
structured clinical interview. We calculated the following syndromes based on the five-
factor solution of the PANSS derived from van der Gaag et al. (2006): positive
symptoms, negative symptoms, disorganized symptoms, excitement, and emotional
distress. Please note that PANSS scores were available for 24 patients, because some
patients at first took part in the action memory task and were then were not available
due to unexpected discharge from the ward.
2.3. Action memory task
The action memory task was directly derived from a previous study (Moritz et al.,
2009) and was translated into Polish by the first author. Participants were individually
tested in a quiet room by the first author.
Participants were presented either verbal instructions or nonverbal pictograms for
actions in the learning phase. Instructions set in a green frame had to be performed by
the participant (actions involving one extremity could be performed with either the left
or right arm/leg/hand/foot), whereas action instructions set in a red frame had to be
imagined but not performed. Before the experiment, participants were instructed to
later recollect the presented actions and to distinguish whether the action was
imagined or performed by them.
Then there was a short practice trial to acquaint participants with the task
requirements. In the main phase, 18 verbal and 18 nonverbal action instructions were
presented, with each part (9 items each) requiring the participant to either perform or
imagine each item. A computer screen displayed each instruction once, for exactly 10 s.
Before recognition, we administered a filler task that took 10 min. Then, 36 verbal
instructions for the studied items were presented along with 20 new action instructions
(the recognition items were presented in a different font from the encoding items to
preventphysicalmatching).Threeresponseswererequired:1.whetherthecorresponding
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instruction had appeared either as text (verbal), pictogram (nonverbal), or was new
(presentation type differentiation); 2. a confidence rating on a 4-point scale ranging from
100% certain (response=1) to extremely uncertain (response=4); 3. participants were
asked to judge whether or not action was performed or imagined (self-monitoring) and
again graded for confidence (100% certain versus uncertain). All items were randomized
both in the learning and recognition phase.
3. Results
3.1. Sociodemographic characteristics
Demographic and psychopathological characteristics are presented
in Table 1. There were nodifferences inage or years of formaleducation
inthetwogroups.However,groupsdifferedingenderdistribution,with
a greater number of males (9/23) in the group with schizophrenia,
χ2(1)=6.12, Pb0.05 and females (11/21) in the healthy control group,
χ2(1)=3.12, P=0.08.
3.2. Action memory recognition accuracy
Before we analyzed specific source memory misattributions, we
determined signal detection parameters. Detection sensitivity was
significantly lower in the group with schizophrenia than in the
healthy group t(62)=3.09, Pb0.01 (M=0.74, S.D.=0.85 and
M=1.34, S.D.=0.70 respectively). Further, a response bias was
calculated with a c index. The c index was calculated with the
following formula: c=−[z(H)+z(F)]/2. Please note that z(H) refers
to standardized z-score for hits, and z(F) refers to standardized z-
score for false alarms. Significantly higher (positive) values of the c
index were found in the group with schizophrenia, indicating that
this group more often than healthy persons responded “new action”,
t(62)=2.72, Pb0.01 (M=0.59, S.D.=0.05 and M=0.32, S.D.=0.23
respectively). An increase in a correct rejection while the extent of
misses increased simultaneously was a consequence of the response
bias, which was intensified in the group with schizophrenia.
Patients did not differ from the healthy group concerning correct
neweventsrecognition,t(62)=0.55,PN0.5.However,theypresenteda
trend toward misperceiving new actions as performed, t(34.08)=1.94,
P=0.06. There were no group differences with regard to new verbal
items and new nonverbal item misattributions. Specific misattribution
patternswerecalculatedandarepresentedinthefollowingparagraphs.
3.3. Self-monitoring for action: Imagined versus performed action
We were interested in between-group differences for self-
monitoring for action attributions. We performed a 2 (two types of
misattribution: performed misattributed as imagined and vice
versa)×2 (verbally vs. nonverbally presented items)×2 (group with
schizophreniavs.healthygroup)ANOVA.Themaineffectofgroupwas
significant, F(1, 62)=14.35, Pb0.001. The two-way interaction
between group and misattribution pattern was insignificant, F(1,
62)=1.94, PN0.1. However, the three-way interaction for event
presentation type×misattribution pattern×group achieved a signif-
icant level, F(1, 62)=4.73, Pb0.05, indicating that the type of
stimulus presentation determined the misattribution pattern.
Several t-tests were calculated to uncover specific between-group
differencesinmisattributionpatterns.Ingeneral,patientsmoreoftenthan
thecontrolgroup perceived imaginedactions as performed,t(32)=2.11,
Pb0.05, and the same pattern was observed for the opposite misattribu-
tion pattern, t(36.67)=3.27, Pb0.01. Patients significantly more often
than healthy participants misattributed verbally presented actions that
had to be performed as being imagined, t(62)=2.94, Pb0.001. However,
nodifferencebetweengroupswasfoundformisattributionofactionsthat
werepresentednonverbally.Ontheotherhand,patientsmorefrequently
than healthy subjects misclassified imagined actions as being performed,
both when verbally, t(39.02)=3.21, Pb0.01, and nonverbally presented,
t(38.09)=2.91, Pb0.01.
Next, we calculated the number of misses (i.e., presented actions
that were misattributed as new). Types of missed response (per-
formed actions misattributed as new; imagined actions misattributed
as new) and presentation type (verbal vs. nonverbal) served as
within-subject factors while groups was the between-subject factor.
The main group effect was significant, F(1, 62)=20.96, Pb0.001. The
two-way interaction between type of missed responses and group, as
well as the three-way interaction between type of missed response,
presentation type and group was insignificant. Still, t-tests indicated
that persons with schizophrenia misattributed performed actions as
being new both when presented nonverbally, t(62)=4.04, Pb0.001,
and verbally, t(62)=3.52, Pb0.001, more often than did the controls.
In contrast, nonverbally but not verbally presented actions that had to
be imagined were more often misperceived as new by patients than
by healthy participants, t(62)=4.00, Pb0.001. The results are
presented in Fig. 1.
3.4. Response confidence for self-monitoring for action
We checked for differences between groups in regards to response
confidencefortheself-monitoringforactionattributions.Patientsmore
often made incorrect “sure” self-monitoring for action attributions
compared with the healthy group, t(39,84)=2.87, Pb0.05. On the
other hand, patients made less frequent correct “sure” self-monitoring
for action attributions than controls, t(62)=7.08, Pb0.001. In line with
previous findings these results suggest that high confidence responses
were observed in the group with schizophrenia more often than in
healthy controls for incorrect, but not for correct attributions.
Concerning correct “unsure” self-monitoring for action attributions,
no differences were found between groups, t(54,79)=1.07, PN0.2.
Patients made more incorrect “unsure” self-monitoring for action
attributions than the healthy group, but the difference remained at a
trend level, t(62)=1.74, P=0.08. Fig. 2 presents the results.
3.5. Action's presentation type: Verbal versus nonverbal discrimination
In the next step of analyses, group differences were investigated to
discriminate between verbally and nonverbally presented actions. Only
Table 1
Demographic and psychopathological characteristics of the groups. Mean and standard deviation are given.
Variables Group with schizophrenia (n=32) (9 female, 23 male) Healthy group (n=32) (21 female, 11 male)
Age
Years of education
PANSS
Positive symptoms
Negative symptoms
Disorganized symptoms
Excitement
Emotional distress
PANSS total rating
32.81 (8.36)
11.78 (0.75)
31.78 (11.67)
12.00 (1.57)
13.20 (5.36)
19.54 (6.89)
18.54 (5.33)
12.91 (3.22)
14.75 (4.34)
72.00 (13.21)
–
–
–
–
–
–
Note: PANSS — Positive and Negative Syndrome Scale. PANSS scores were calculated according to van der Gaag et al. (2006) five factor model.
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misattributionswereanalyzed.A2×2×2mixedANOVAwasconducted
with misattribution type (verbally presented material attributed as
nonverbal and vice versa), performance type (imagined vs. performed
actions) asthewithin-subjectfactors andgroupasthebetween-subject
factor. The main group effect was insignificant, F(1,62)=1.96, PN0.1.
However, a two-way interaction between misattribution type and
group was significant, F(1, 62)=8.40, Pb0.01. In addition, a three-way
interactionbetweenperformancetype(imaginedvs.performedactions),
misattribution type, and group was also significant, F(1, 62)=4.03,
Pb0.05.
To calculate differences between groups for specific misattribution
patterns, several t-tests were conducted. When considering actions
that had to be imagined, patients misperceived verbally presented
actions as being presented nonverbally, t(62)=2.56, Pb0.05, signif-
icantly more often than healthy subjects. The reverse misattribution
pattern for imaginedactionswas also observedmore often in patients,
t(62)=2.36, Pb0.05. However, with regard to actions that had to be
performed, patients and healthy subjects comparably differentiated
actions that were presented nonverbally from those that were
presented verbally (PN0.05). Results are presented in Fig. 3. The
misattributions of target action to neware calculated and presentedat
the end of Section 3.3.
3.6. Cognitive confidence for verbal vs. nonverbal discrimination
We were further interested in confidence responses for discrimina-
tion between verbally and nonverbally administered actions. Both
correctandincorrectattributionsaccompaniedbyhigh-confidentratings
were calculated. Persons with schizophrenia made far fewer correct
high-confidence attributions than healthy participants, t(55,11)=4.07,
Pb0.001, and at the same time, patients made more incorrect high-
confidence responses than controls, t(46,48)=2.07, Pb0.05. Results are
presented in Fig. 4.
Finally, the proportion of high-confident false responses to the
total number of all high-confident responses was calculated, which is
referred to the knowledge corruption index (Moritz and Woodward,
2006). The knowledge corruption index was 40.7% in patients relative
to 22.7% in healthy participants, t(57)=4.87, Pb0.001. The implica-
tion of these results is that persons with schizophrenia are more
convinced that their answers are correct when in fact they are wrong.
3.7. Correlations between psychopathology, source monitoring and
metamemory
The subscale scores of the PANSS were correlated with correct vs.
incorrect self-monitoring for actions attributions (performed vs.
imagined action). No significant relation emerged. There was also
no significant correlation between presentation type discrimination
(verbal vs. nonverbal) and psychopathology. Hence, the results
suggest that neither self-monitoring for action nor differentiation
between action presentation type errors is related to any specific
schizophrenia symptom.
0
1
2
3
4
5
6
Imagined to
performed
performed to
imagined
new to
performed
new to
imagined
Imagined to
performed
performed to
imagined
new to
performed
new to
imagined
performed to
new
imagined to
new
non-verbal verbal
Healthy group
Group with schizophrenia
% of total responses
Attribution
Source
Presentation
type
***
***
***
***
**
**
P= 0.06
new
Fig. 1. Comparisonontherateofincorrectself-monitoringfor actionsresponseswith respecttopresentationtype(verballyvs.non-verballypresentedactions).The proportionof
misattributionstototalresponsesispresented.Ingeneral,thegroupwithschizophreniamorefrequentlythanthehealthygroupmisperceivedimaginedactionsasperformedand
vice versa.Patients alsocommittedmoremissesandhadthe tendencytoguessperformedactions(more misattributionsofnewactiontoperform).Note:*— Pb0.05,**— Pb0.01,
*** — Pb0.001.
0
5
10
15
20
25
30
35
40
sureunsure sureunsure
correct self-monitoring attributions incorrect self-monitoring attributions
% of total responses
***
*
P= 0.08
Healthy group
Group with schizophrenia
Fig. 2. Group differences in cognitive confidence for correct and incorrect internal
source attributions. The proportion of correct and incorrect attributions to total
responses is presented. Patients made a smaller number of correct “sure” answers
than controls and at the same time they made more incorrect “sure” attributions.
Note: * — Pb0.05, *** — Pb0.001.
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The only relationship between emotional distress measured with
the PANSS and the confidence ratings for incorrect attributions was
significant (r=0.44, Pb0.05). For a detailed correlation matrix see
Table 2.
4. Discussion
Our study examined whether persons with schizophrenia have
more difficulties than healthy controls regarding self-monitoring for
actions (the memory discrimination of imagined versus performed
actions) and memory discrimination for verbally versus nonverbally
presented actions. For the first time, cognitive confidence was
assessed for both types of source monitoring.
In general, patients were less sensitive for correct recognitions as
indexed with the d′ signal detection parameter. They also displayed a
greater tendency to judge items as new as evidenced by the signal
detection parameter c. It was found that patients made significantly
more errors for self-monitoring for actions. Patients also made
significantly more incorrect attributions when asked to differentiate
between verbally and nonverbally administered actions. Importantly,
recognition of new actions was comparable between groups, except
for a higher tendency in patients to misattribute some new actions as
being performed.
It was also found that persons with schizophrenia were more
susceptible than healthy subjects to misattributions concerning self-
monitoring for action in that they regularly misclassified imagined
actions as being performed, as well as performed actions as being
imagined. This result confirmed our hypothesis and is consistent with
prior studies reporting similar self-monitoring deficits for actions
among psychosis-prone subjects (Laroi et al., 2005; Peters et al.,
2007). Similar results regarding former misattribution patterns were
obtained by Mammarella et al. (2010) in schizophrenia, although this
study did not address misperception of performed actions as imagined.
Interestingly, misattribution in which patients misperceived performed
actions as imagined, but not the reverse, was influenced by the action's
presentationtypeandwasfoundonlyforverballypresentedstimulibut
not for nonverbally presented stimuli.
Concerning presentation type differentiation, it was found that
patients more than healthy subjects confused verbally presented
actions with those presented nonverbally and vice versa. This is in line
with prior studies that have found that people with schizophrenia
have problems in differentiating between two external sources (e.g.
Keefe et al., 1999). Unlike with self-monitoring for action errors, there
were no differences between groups in guessing verbal or nonverbal
actions (no differences in new actions attributed as verbal or
nonverbal). Using the same action memory task Moritz et al. (2009)
found that patients with obsessive-compulsive disorder made fewer
correct attributions for nonverbally presented actions than did
healthy subjects. In our study we found an interaction between
presentation type (verbal vs. nonverbal actions), performance type
(imagined vs. performed actions), and group indicating that increases
in confusions about verbal and nonverbal material in the group with
schizophrenia occurred only when actions were imagined, but not
when actions were performed. This suggests that patients better
remembered enacted actions than those being imagined, which is
consistent with studies in healthy people (e.g. Helstrup, 2004) as well
as among persons with schizophrenia (Brodeur et al., 2009;
Mammarella et al., 2010).
Our results tentatively suggest a rather general source monitoring
deficit in schizophrenia, which is consistent with some previous
findings (e.g. Keefe et al., 1999). However, other biased response
patterns that were observed among persons with schizophrenia may
0
1
2
3
4
5
6
7
8
9
verbal to
non-verbal
non-verbal
to verbal
new to
non-verbal
new to
verbal
verbal to
non-verbal
non-verbal
to verbal
new to
non-verbal
new to
verbal
non-verbal
to new
verbal to
new
New PerformedImagined
% of total responses
Attribution
Source
Performance
type
*
*
***
***
***
Healthy group
Group with schizophrenia
Fig. 3. Group differences regarding incorrect differentiation between verbal and non-verbal actions with respect to performance type (imagined vs. performed). The proportion of
misattribution to total responses is presented. The group with schizophrenia made more incorrect source attributions than the healthy group but only for imagined actions. The
group with schizophrenia also committed more misses than healthy participants. Note: * — Pb0.05, *** — Pb0.001.
0
5
10
15
20
25
30
35
40
45
50
high confident correct
attribution
hight confident incorrect
attribution
Healthy group
Group with
schizophrenia
***
*
% of total responses
Fig. 4. Group differences on incorrect and correct differentiation between high
confident verbal and nonverbal actions. Percentages of total responses are presented.
Note: * — Pb0.05, *** — Pb0.001.
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Page 6

reflect more general memory dysfunctions (for review see Reichenberg
and Harvey, 2007). Consistent with previous studies (e.g. Moritz and
Woodward, 2005; Mammarella et al., 2010), it wasfound that there is a
greater tendency to produce misses (misperception of old actions as
newones)bypatients.Inaddition,patientscommonlyjudgedanitemas
new, a pattern that enhanced both the rate of misses and correct
rejections. Our results also showed an increased guessing strategy for
some performed actions (false alarm: new actions attributed as
performed) by patients, which may also exaggerate self-monitoring
for actions biases. Other false alarms were not found, which suggests
that false alarms are not elevated in schizophrenia. This is consistent
with previous source monitoring studies (e.g. Moritz and Woodward,
2005; Mammarella et al., 2010) as well as other cognitive studies (e.g.
Schwartz et al., 2009).
While our results are congruent with our assumption that persons
with schizophrenia present source monitoring for actions deficits, the
nature of these need further empirical explanation. One of the possible
mechanisms that underlie self-monitoring for action deficits in
schizophrenia may be impaired action processing that was found in
this group (Frith et al., 2000a,b; Franck et al., 2001; Turken et al., 2003).
Due to the lack of contextual information about produced actions
(e.g.kinestheticinformationaboutspecificpositionofthearm),patients
may not have detaileddata thatare critical todiscriminatea new action
(e.g. “Close your eyes with your hand”) from an old one (e.g. “Put your
hand on a forehead”). For the same reason, patients may misattribute
performed actions with those that had to be imagined. Moreover, self-
monitoring biases may be also influenced by an enhanced imagery
vividness that is frequently observed in schizophrenia (Mintz and
Alpert, 1972; Aleman et al., 2002; Sack et al., 2005; Ortel et al., 2009).
Previous studies have found that source monitoring errors may be
exaggerated by an imbalance between imagery and reality both in
healthy subjects (Johnson et al., 1979, 1988) and in persons with
schizophrenia (Böcker et al., 2000; Aleman et al., 2002). Finally, some
neuroimaging studies have reported that the frontal lobes are involved
in source monitoring (Mitchell et al., 2004; for review, see Mitchell and
Johnson, 2009). In addition it was found that self-monitoring engages
thefrontallobes,thethalamus,andthecerebellum(Simonsetal.,2006).
These structures operate, however, in a dysfunctional way in schizo-
phrenia(Torreetal.,2005)andthusmaybeconsideredasaneuralbasis
for cognitive impairments, including self-monitoring for this popula-
tion. However, the mechanisms outlined above were not empirically
verified, leaving the general question of the causal mechanisms of poor
self-monitoring and source monitoring in schizophrenia unresolved.
Another important set of findings relates to response confidence.
Consistent with our hypothesis and previous findings (Moritz and
Woodward, 2002; Moritz et al., 2005; Glöckner and Moritz, 2009), we
found disrupted cognitive confidence for different aspects of the source
monitoring in the group with schizophrenia. The results suggest that
patients put more trust in false self-monitoring for actions than healthy
participants. At the same time, both groups did not differ concerning
“unsure”correctattributions,whichisnotfullyconsistentwithprevious
studiesdetectinglessconfidenceincorrectresponses.Ourfindingsarein
line with the notion that psychotic patients not only exhibit cognitive
distortions, but simultaneously hold their beliefs with absolute
confidence and resistance to alternative evidence (e.g. bias against
disconfirmatory evidence) (Moritz and Woodward, 2006; Woodward
etal.,2006).Greaterknowledgecorruptionwasfoundforpatientswitha
higher proportion of incorrect high-confidence responses, again in
accordancewithpreviousstudies(forreviewseeMoritzandWoodward,
2006).However,comparedtopreviousstudiesitappearsthatdeviances
of cognitive confidence found in the present study were weaker, which
may be due to the differences in the material used across studies and
heterogeneous samples.
Finally, challenging the view that source monitoring is related to
the symptoms of schizophrenia, we were not able to find that any of
our source monitoring indexes were related to the specific symptoms
of schizophrenia assessed with the PANSS five-factor model. This is in
line with some studies (e.g. Vinogradov et al., 1997), but not with
others that detected a relationship between source misattributions
and symptoms of schizophrenia (e.g. Brunelin et al., 2006; Johns et al.,
2006; Anselmetti et al., 2007; Startup et al., 2008). Mammarella et al.
(2010) found that misattribution of imagined actions as performed
was correlated with formal thought disorder, which is however
inconsistent with our results showing no relation between action self-
monitoring errors and disorganization. Inconsistencies across studies
may be caused by different symptom assessments, as well as the
heterogeneous cognitive tasks (i.e. differences in time between
learning phase and recognition). Only cognitive confidence for
incorrect responses (r=0.44, Pb0.05) was significantly correlated
with the emotional distress subscale of the PANSS. Consistent with
this finding, a recent study on obsessive-compulsive patients revealed
that decreased cognitive confidence is accompanied with anxiety and
depression (Nadeljkowic et al., 2009). These results should be
considered as preliminary due to the small sample and other
limitations that were discussed below.
Before turning to the final conclusions, some limitations of our
study have to be brought to the reader's attention. Most importantly,
our results concerning the relationship between source monitoring
and psychopathology must be considered preliminary because of two
main limitations. First, results were computed for a rather small
sample of patients (n=24) and are in need of replicationwith a larger
sample. Further, even though the PANSS (Kay et al., 1986) is the gold-
standard symptoms assessment in schizophrenia, it does not allow a
detailed description of the symptom's qualitative features. Hence, to
shed more light on the relationship between specific symptoms and
source monitoring, it may be necessary to administer a more fine-
grained instrument for future studies (e.g., the Psychotic Symptoms
Rating Scale (Haddock et al., 1999) or the Scales for the Assessment of
Positive (Andreasen, 1984a) and Negative Symptoms (Andreasen,
1984b), which tap into detailed aspects of positive and negative
symptoms). The relationship between specific symptoms and source
monitoring may be addressed in future studies by between-subjects
comparisons (patients with different symptoms classes). Finally,
there were some differences in the gender distribution between
Table 2
Correlation matrix for source attributions, metamemory variables and psychopathology (PANSS) (n=24).
VariablesPositive symptoms Negative symptomsDisorganized symptomsExcitement Emotional distressTotal score
Correct self-monitoring attributions
Incorrect self-monitoring attributions
Correct presentation type attributions
Incorrect presentation type attributions
Knowledge corruption
Confidence for incorrect decisions
Confidence for correct decisions
0.10
−0.19
0.07
−0.16
0.14
0.11
0.04
0.03
−0.23
0.12
−0.15
0.13
0.19
−0.07
0.04
0.12
0.04
−0.14
0.09
0.06
−0.07
−0.13
0.44⁎
0.28
−0.15
0.06
−0.05
0.03
0.04
0.12
0.13
−0.33
0.36
−0.36
−0.34
0.08
0.05
−0.16
0.12
0.15
0.29
0.30
Note: Self-monitoring attributions refer to a discrimination between performed and imagined actions. Presentation type attributions refer to a discrimination between verbally and
nonverbally presented actions.
⁎ Pb0.05.
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Page 7

groups, which were however comparable to the sample assessed by
Mammarella et al. (2010). To the best of our knowledge, there
currently is no study that addresses gender differences in source
monitoring; thus, conclusions about the influence of gender on our
study cannot be drawn.
To conclude, despite these limitations, our findings are promising
and support the hypothesis that self-monitoring for actions is impaired
in schizophrenia. At the same time patients had difficulties in
distinguishing across very different types of stimuli and response
requirements which tentatively speaks to a rather general source
monitoring deficit. Symptoms were not found to be related to any type
of source monitoring; however, these results may be limited by a
relatively small and heterogeneous sample. Thus a replication on a
larger sample study is required. Finally, our findings revealed an
impaired modulation of cognitive confidence among patients who
tended to be overconfident in errors on some parameters. Our study is
silent about the influence of source monitoring on the specific
symptoms of schizophrenia and the underlying mechanisms of source
monitoring.The causalrole of sourcemonitoringonsymptoms canbest
be established with a longitudinal study in the future. Future research
may benefit from investigating different underlying mechanisms of
source monitoring deficits (e.g. the role of neurocognitive functioning,
the role of imagery vividness in self-monitoring or the role of action
processing in action source monitoring) in schizophrenia.
Acknowledgments
This study is a part of first author's (Ł.G.) PhD project supervised by Prof. Andrzej
Kokoszka. The authors wish to thank Prof. Jacek Wciórka and Janusz Szymański from
Psychiatry Clinic I, Institute of Psychiatry and Neurology, Warsaw, for help in the
recruitment the study participants. The authors also are grateful to Mrs. Amanda
Brooks, who proofread an earlier version of the manuscript. The authors would like to
express their gratitude to the participants who took part in the study.
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