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Neuropsychological
Rehabilitation: An International
Journal
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and subscription information:
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The effects of verbalisation

on cognitive performance in
schizophrenia: A pilot study
using tasks from the Delis
Kaplan Executive Function
System
a b
Kirsty E. Harvey , Professor Cherrie A. Galletly ,
a a
Colin Field & Michael Proeve
a
School of Psychology, University of South Australia ,
Adelaide, South Australia, Australia
b
Discipline of Psychiatry, School of Medicine,
University of Adelaide , South Australia, Australia
Published online: 02 Sep 2009.

To cite this article: Kirsty E. Harvey , Professor Cherrie A. Galletly , Colin Field
& Michael Proeve (2009) The effects of verbalisation on cognitive performance in
schizophrenia: A pilot study using tasks from the Delis Kaplan Executive Function
System, Neuropsychological Rehabilitation: An International Journal, 19:5, 733-741,
DOI: 10.1080/09602010902732892
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 NEUROPSYCHOLOGICAL REHABILITATION
2009, 19 (5), 733– 741

The effects of verbalisation on cognitive performance

in schizophrenia: A pilot study using tasks from the
Delis Kaplan Executive Function System
Downloaded by [Washington University in St Louis] at 16:26 08 October 2014

Kirsty E. Harvey1, Cherrie A. Galletly2, Colin Field1, and

Michael Proeve1
1
School of Psychology, University of South Australia, Adelaide, South Australia,
Australia; 2Discipline of Psychiatry, School of Medicine, University of Adelaide,
South Australia, Australia

Cognitive impairment is common in schizophrenia, and has adverse effects on

functional outcome. Cognitive remediation strategies in which people with
schizophrenia speak aloud (verbalise) during task performance have demon-
strated some success in improving performance on the Wisconsin Card Sorting
Test. This study extends previous research by assessing whether verbalisation
also improves performance on tasks selected from the Delis-Kaplan Executive
Function System (D-KEFS).
Twenty two subjects with schizophrenia participated in the study. We used a
within subjects design to compare performance on the D-KEFS Tower Test and
Trail Making Test when participants (a) produced concurrent verbalisation, or (b)
remained silent.
Results demonstrated selective benefits of verbalisation on a neuropsychologi-
cal task requiring multiple executive functions (number-letter switching task),
while performance on tasks requiring simpler single-component cognitive func-
tions (visual scanning and motor speed tasks) was adversely affected.
The effects of verbalisation on the cognitive task performance of patients with
schizophrenia differ depending on the nature of the task. Benefits are seen in tests
of executive skills but performance worsens in single component cognitive tasks.
When developing cognitive remediation strategies for people with schizo-
phrenia, consideration should be given to the nature and cognitive demands of
each task before recommending verbalisation strategies.

Correspondence should be sent to Professor Cherrie Galletly, Discipline of Psychiatry,

School of Medicine, Suite 13, The Adelaide Clinic, 33 Park Tce, Gilberton 5081. South
Australia. E-mail: cherrie.galletly@adelaide.edu.au

# 2009 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business
http://www.psypress.com/neurorehab DOI:10.1080/09602010902732892
 734 HARVEY ET AL.

Keywords: Neuropsychology; Verbal Learning; Vocalisation; Rehabilitation;

Memory; Psychotic disorders.

INTRODUCTION
People with schizophrenia typically have deficits in multiple domains of cog-
nitive function, and the severity of cognitive dysfunction is an important pre-
dictor of functional outcome (Green, Kern, Braff, & Mintz, 2000; Holthausen
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et al., 2007). The development of interventions to improve cognitive function

in schizophrenia is now regarded as a priority (Kraus & Keefe, 2007). The
novel antipsychotic drugs are associated with modest improvement in cogni-
tion (Galletly, Clark, McFarlane, & Weber, 2000; Keefe, Silva, Perkins, &
Lieberman, 1999), but recently there has been concern about the role of prac-
tice effects in these studies (Szöke & Trandafir, 2008; Goldberg et al., 2007).
A number of drugs which may have the potential to enhance cognition in
schizophrenia are currently being evaluated (Galletly, 2008). However,
non-pharmacological interventions are clearly also important. A recent
meta-analysis by McGurk, Twamley, Sitzer, McHugo, and Mueser (2007)
found that cognitive remediation therapy (CRT) resulted in significant
improvement in cognition in schizophrenia, with a mean effect size of 0.41
for global cognitive performance.
CRT in schizophrenia utilises many different approaches, ranging from
computer games to individual remedial work with a psychologist (McGurk
et al., 2007). It would be helpful to have strategies that could be adopted
easily, without requiring intensive resources. One possible strategy is to encou-
rage people with schizophrenia to speak out loud, describing the steps as they
go along, while they undertake tasks. More than 30 years ago, it was proposed
that verbalising a behavioural strategy might decrease distractibility in people
with schizophrenia (Meichenbaum & Cameron, 1973). Another possibility is
that schizophrenia is associated with an impaired ability to use deductive top
down cognitive strategies (John & Hemsley, 1992), and that vocally expressing
the criteria used to make classification decisions guides participants to develop
a top down cognitive strategy that leads to better information processing and
task performance (Stratta et al., 1997).
There is now considerable evidence that verbalisation (also termed
vocalisation in some studies) is the most effective means for people with
schizophrenia to improve their performance on the Wisconsin Card Sorting
Test (WCST, Berg, 1948) (Choi & Kurtz, in press; Perry, Potterat, & Braff,
2001; Rossell & David, 1997; Rossi et al., 2006). Rossi et al. investigated
the association between the ability to improve WCST performance using ver-
balisation, and the type of antipsychotic drug prescribed. They found that,
among participants who had impaired WCST performance at baseline,
 VERBALISATION: COGNITIVE GAIN IN SCHIZOPHRENIA 735

there was more likelihood of improved performance using the verbalisation

technique in participants taking atypical antipsychotic drugs, compared to
those taking conventional antipsychotics.
However, there is a lack of studies evaluating the efficacy of verbalisation
strategies in improving performance on tasks other than the WCST. This is
clearly important, as hopefully, verbalisation may be a simple CRT technique
that could be widely adopted in rehabilitation programmes for people with
schizophrenia.
We selected the Trail Making Test and the Tower Test from the Delis-
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Kaplan Executive Function System (D-KEFS; Delis, Kaplan, & Kramer,

2001). Recent studies have confirmed the efficacy of these measures from
the Delis-Kaplan scale in people with schizophrenia (Lysaker, Whitney, &
Davis, 2006; Lysaker et al., 2008). The tasks selected are similar to the
WCST in that they measure executive functioning; people with schizophrenia
typically perform poorly on them; and they are conducive to verbalisation of
the steps required to undertake the tasks.
We extended previous research by employing a design that enabled us to
compare verbalising and non-verbalising strategies for each task and to
control for practice effects. The importance of practice effects in studies of
cognition in schizophrenia has been highlighted recently (Goldberg et al.,
2007; Szöke & Trandafir, 2008). We used a within-subjects design, important
given the heterogeneity in cognitive abilities and learning potential evident in
schizophrenia (Kurtz & Wexler, 2006). Based on previous findings (Choi &
Kurtz, 2008; Rossi et al., 2006; Stratta et al., 1997) with the WCST, we
hypothesised that the verbalising condition would be associated with better
performance on the D-KEFS Trail Making and Tower Tests.

METHOD

Participants
Twenty two participants were recruited from the Lyell McEwin Health
Service (n ¼ 20), a community-based mental health service, and the
Mental Illness Fellowship (n ¼ 2), a consumer and carer organisation, in
Adelaide, Australia. They were all between 18 and 65 years of age and
fluent in English. They met DSM-IV criteria for schizophrenia and were
stabilised on atypical antipsychotic medications (risperidone, olanzapine or
clozapine). No participant had a history of traumatic brain injury, intellectual
disability or neurological disorder.
After giving informed consent, participants were randomly allocated to
Condition 1 (n ¼ 12; 8 male and 4 female) or Condition 2 (10 males).
 736 HARVEY ET AL.

The study was approved by the Human Ethics Committee of the North West
Adelaide Health Service.

Materials
Two tasks from the D-KEFS were used. The Tower Test assesses spatial
planning, rule learning, inhibition of impulsive and preservative responding,
and the ability to establish and maintain the instructional set. The Trail
Making Test is a five condition task that assesses flexibility of thought on a
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visual-motor sequencing task. Key component processes necessary for per-

forming this task include visual scanning, number sequencing, letter sequen-
cing and motor speed. The National Adult Reading Test (NART; Nelson &
Willison, 1991) was used to assess premorbid intelligence.

Design
A mixed factorial design was employed. Participants were randomly assigned
to one of two conditions: Condition 1 (Tower Test nonverbalising, Trail
Making verbalising), or Condition 2 (Tower Test verbalising, Trail Making
nonverbalising).

Statistics
A mixed ANOVA, with Condition as a between participants factor and Task
Type as a within participants factor, was used to examine whether verbalising
ongoing actions was associated with better task performance.

Procedure
Participants were first tested on the D-KEFS Tower Test. This test was admi-
nistered in accordance with either the standard procedure or the modified pro-
cedure, depending on the participant’s group membership (Condition 1 or
Condition 2). For the modified procedure, participants were asked to com-
plete the test in the same way as for the standard procedure except that
they were asked to verbalise their thought processes as they performed the
test. Participants then answered a series of questions concerning personal
information (e.g., age, education, previous number of hospitalisations) in
order to enhance distraction from the previous task. The D-KEFS Trail
Making Test was then administered according either to the standard or modi-
fied (verbalising) procedure, depending on Condition membership. Accord-
ing to the modified procedure, participants were asked to verbalise their
thought processes as they performed the test. Finally, participants completed
the NART. All D-KEFS tasks were scored, converted to standard scores and
scaled. The testing sessions lasted for 60– 70 minutes, which was within the
capability of all participants.
 VERBALISATION: COGNITIVE GAIN IN SCHIZOPHRENIA 737

RESULTS
As shown in Table 1, using the t-test for independent samples and a signifi-
cance level of .05, there were no significant between condition differences
in age, t(20) ¼ 0.42, p ¼ .85; education, t(20) ¼ – 0.46, p ¼ .86;
symptom duration, t(20) ¼ 1.23, p ¼ .27; number of past hospitalisations,
t(20) ¼ 0.73, p ¼ .47; or premorbid IQ, t(20) ¼ –0.53, p ¼ .64.

TABLE 1
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Participant characteristics (mean+SD) for Condition 1 (Tower Test nonvocal/Trail

Making Test vocal) and Condition 2 (Tower Test vocal/Trail Making Test nonvocal).

Condition 1 Condition 2

Age (years) 35.50 + 7.00 34.10 + 8.84

Education year level 10.25 + 1.14 10.50 + 1.43
Illness duration (years) 12.50 + 7.56 8.38 + 6.02
Number of past hospitalisations 4.67 + 1.83 4.00 + 2.08
Premorbid IQ estimate (NART) 102.99 + 6.48 104.51 + 6.91

NART, National Adult Reading Test; SD, standard deviation.

TABLE 2
DKEFS Scale Scores (mean+SD) on the Tower Test and Trail Making Test for Condition 1
(Tower Test nonvocal/Trail Making Test vocal) and Condition 2 (Tower Test vocal/Trail
Making Test nonvocal)

ANOVA comparing
Condition Mean score† groups

Tower Achievement Total Condition 1 7.58 + 2.28

Condition 2 7.20 + 2.30 n.s.
Trails 1 Visual Scanning Condition 1 2.92 + 3.68
Condition 2 8.80 + 2.78 F(1, 20) ¼ 17.28,
p ¼ .0004
Trails 2 Number Sequencing Condition 1 4.75 + 4.05
Condition 2 5.30 + 2.98 n.s.
Trails 3 Letter Sequencing Condition 1 4.67 + 3.55
Condition 2 6.30 + 4.03 n.s.
Trails 4 Number/Letter Sequencing Condition 1 6.75 + 3.19
Condition 2 4.00 + 2.94 F(1, 20) ¼ 4.34,
p ¼ .05
Trails 5 Motor Speed Condition 1 6.92 + 2.90
Condition 2 10.00 + 1.70 F(1, 20) ¼ 8.72,
p ¼ .009

† Higher scores indicate better performance. Mean and standard deviation scores for the normal
population are 10 and 3, respectively.
ANOVA, analysis of variance; DKEFS, Delis-Kaplan Executive Function System; n.s., non-
significant; SD, standard deviation.
 738 HARVEY ET AL.

Participant results, expressed in standard scores, for the Tower Test and
Trail Making Test are shown in Table 2. Participants performed well below
average for the standard condition in some tasks, including the Trail
Making number sequencing and number/letter sequencing.
There was a significant main effect of Task Type, F(5, 16) ¼ 8.45,
p ¼ .0006. In addition, there was a significant interaction between Task
Type and Condition, F(5, 16) ¼ 4.70, p ¼ .009. In order to ascertain the
source of the interaction, planned comparisons were performed between Con-
ditions 1 and 2 for each cognitive task (Table 2). Consistent with the hypoth-
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esised benefits of verbalisation, Condition 1 participants acquired

significantly higher scores than Condition 2 participants on the Trails
Number-Letter Sequencing Task, F(1, 20) ¼ 4.34, p ¼ .05. However, Con-
dition 2 participants acquired significantly higher scores than Condition 1 par-
ticipants on the Trails Visual Scanning Test, F(1, 20) ¼ 17.28, p ¼ .0004;
and the Trails Motor Speed Task, F(1, 20) ¼ 8.72, p ¼ .009.

DISCUSSION
These results show that verbalising ongoing actions was an effective method
for enhancing performance on a difficult task that requires multiple executive
functions (the number-letter switching task). However, verbalising actions
appeared to hinder performance on simpler cognitive tasks requiring single
component skills (visual scanning and motor speed tasks).
It appears that with easier tasks the variability in participants’ performance
depends more upon speed than accuracy, as all participants can achieve high
accuracy. Therefore, verbalising easy tasks may not help improve perform-
ance as speed is impaired by the additional task of having to verbalise
actions. On more difficult tasks, verbalising may be beneficial by improving
accuracy. The selective benefits of the verbalisation strategy on the number-
letter switching task may occur because this task utilises higher order execu-
tive functions (cognitive flexibility, working memory, visual-motor sequen-
cing) than the other trail making tasks. Verbalising ongoing actions may
have guided participants to use a cognitive strategy that allowed for better
conceptual organisation.
Verbalising ongoing actions may also have been beneficial by decreasing
distractibility on tasks where greater concentration and attention is required
(Meichenbaum & Cameron, 1973). Distraction has a less pronounced effect
on simple tasks, where one can often attend to other stimuli as well as com-
plete the task. Indeed, a possible explanation for the finding that poorer per-
formance was associated with the vocal strategy on the single-component
tasks is that verbalising served as a nuisance by disrupting the momentum
of motor skills and automatic visual scanning processes.
 VERBALISATION: COGNITIVE GAIN IN SCHIZOPHRENIA 739

In light of these interpretations, it is reasonable to question why

performance was not enhanced with the verbalisation strategy on the
Tower task, which requires multiple functions, including rule learning, the
ability to plan ahead, and response inhibition (Welsh, Revilla, Strongin, &
Kepler, 2000). In terms of standard scores, performance on the Tower Test
was among the best-performed tasks by participants. In light of previous find-
ings that verbalisation assists performance of the longer and more stressful
WCST (Rossell & David, 1997; Stratta et al., 1997), the following inter-
pretation of the effect of verbalisation is proposed. This group of participants
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with schizophrenia found number/letter sequencing to be difficult, as shown

by their scores under standard conditions (Table 2), and therefore were
assisted by verbalisation. They found Visual Scanning relatively easier, so
that verbalisation interfered with performance. The Tower Test was neither
the most difficult nor the easiest of the cognitive tasks for participants, so
that verbalisation was neither beneficial nor detrimental to their performance
on this task.
The ability to improve WCST performance utilising instruction in schizo-
phrenia has been linked to N-acetylaspartate and glutamate/glutamine levels
in the anterior cingulate cortex (Ohrmann et al., 2008), although this study
used an instruction technique that did not involve verbalisation. It would be
interesting to replicate this study, comparing verbalising and non-verbalising
strategies, to investigate differences in brain function when participants use
different remediation strategies. Besides the findings implicating the anterior
cingulate cortex, there are differences between control and schizophrenia
groups in neuronal integrity in the dorsolateral prefrontal cortex. Schizo-
phrenia is associated with disordered verbal expression (manifest as thought
disorder), the experience of abnormal verbal perceptions (experienced as
auditory hallucinations and thought insertion) and impaired verbal fluency,
learning and memory (Wobrock et al., 2008). It is possible that verbalising
strategies are especially effective in normalising dysfunctional language-
dependent cognitive systems in schizophrenia.
The statistical power of this study was limited by the sample size. We moni-
tored carry-over effects by counterbalancing the type of instruction given
(i.e., verbalising vs nonverbalising) across groups, and ensuring each cogni-
tive task was performed only once. However, a limitation of the design was
that by precluding follow-up assessment on the same task it was unclear
whether benefits in cognitive performance from the verbalising strategy per-
sisted. Additionally, it cannot be certain that learning did not occur, whereby
following the verbal instruction condition participants sub-verbalised on
subsequent tasks when directed no longer to verbalise.
Although we found that verbalisation affected task performance, partici-
pants differed in the amount of verbalisation they used while completing
the tasks. This potential confounding factor could be addressed by either
 740 HARVEY ET AL.

controlling or monitoring and measuring the amount of verbalisation used by

participants during task performance.
The choice of the D-KEFS may also be a limitation of our study. While the
D-KEFS has generally been regarded as having good reliability, recent work
evaluating the reliability and standard error of contrast measures on the
D-KEFS by Crawford, Sutherland, and Garthwaite (2008) does raise some
concerns. It is therefore crucial that verbalisation strategies be evaluated
using a range of other neuropsychological tests in people with schizophrenia.
Results of our study suggest that verbalisation of tasks may not be uncon-
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ditionally helpful in the rehabilitation of schizophrenia. Although verbalisa-

tion may enhance the processing of complex tasks requiring multiple
executive functions, verbalisation may in fact interfere with the completion
of simpler tasks.

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Manuscript received February 2008

Revised manuscript received December 2008
First published online March 2009