schizophrenia

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Verbal Communication Impairments and Cognitive Control Components in People With Schizophrenia

Schizophrenia involves multiple communication impairments, including (a) disorganized speech, or
formal thought disorder (FTD); and (b) decreased speech output, or poverty of speech. Both FTD and
poverty of speech have been hypothesized to be associated with deficits in executive functioning or
cognitive control. The current study examined whether FTD and poverty of speech were differentially
associated with two distinct aspects of cognitive control, working memory and controlled retrieval.
Compared with control participants (n
30), people with schizophrenia (n
47) exhibited poorer
performance on both working memory and controlled retrieval tasks. However, only FTD (and not
poverty of speech) was associated with poor working memory. In contrast, only poverty of speech (and
not FTD) had a significant zero-order association with poor controlled retrieval. At the same time,
working memory and controlled retrieval interacted to predict FTD, with the highest amount of FTD
associated with both poor working memory and poor controlled retrieval. In contrast, psychometric
control tasks were not associated with FTD or poverty of speech. This research suggests that FTD and
poverty of speech are differentially associated with deficits in distinct aspects of cognitive control.
Keywords: schizophrenia, formal thought disorder, poverty of speech, working memory, controlled
retrieval
People with schizophrenia can exhibit multiple communication
impairments. One type of communication impairment is speech
that is difficult to understand or disorganized, or formal thought
disorder (FTD; Andreasen, 1979a). Another type of communication
impairment is decreased verbal productivity, or poverty of
speech (Andreasen, 1979a, 1982). Previous factor analytic research
suggests that FTD and poverty of speech might be distinct
symptoms (e.g., Andreasen, 1979b; Berenbaum, Oltmanns, &
Gottesman, 1985; Harvey et al., 1992; Liddle, 1987). However,
despite evidence for being distinct symptoms, it is not clear
whether FTD and poverty of speech involve deficits in different
cognitive processes (Melinder & Barch, 2003). For example, both
FTD and poverty of speech have been hypothesized to be associated
with deficits in executive functioning or cognitive control
(e.g., Barch & Berenbaum, 1997; Cohen & Servan-Schreiber,
1992; Cohen, Targ, Servan-Schreiber, & Spiegel, 1992; McGrath,
1991). Cognitive control refers to a set of processes involved in
nonautomatic or novel behavior (Botvinick, Braver, Barch, Carter,
& Cohen, 2001). Of importance, cognitive control is a broad
construct with multiple components (e.g., Botvinick et al., 2001).
The current study examined whether FTD and poverty of speech
were differentially associated with distinct aspects of cognitive
control: (a) working memory and (b) controlled retrieval.
Working memory has been defined as the maintenance of a small
amount of information in an active state for ongoing cognitive
operations (Cowan, 2005). Hence, working memory involves both
the temporary storage or maintenance of information and the
active processing or manipulation of information (Baddeley &
Hitch, 1974; Barch, 2005). For example, on the 2-Back task in
which people see a series of letters, people must continuously store
the last two letters that they have seen. While remembering the last
two letters, people must also process information (e.g., compare
the current letter with letters held in memory, remove old items,
update and reorder the items being stored).
Controlled retrieval refers to recollection processes that are
engaged when automatic memory processes are insufficient (e.g.,
in the face of competing information). According to dual-process
models of memory (e.g., Jacoby, 1991; Jacoby, Bishara, Hessels,
& Toth, 2005), recognition memory can be based on automatic
processes or on controlled recollection processes. For example, on
the Sternberg Probe Item Recognition task (Jonides, Smith,
Marshuetz, Koeppe, & Reuter-Lorenz, 1998), participants see a
target set of several letters, and then, after a delay, they see a single
probe letter and decide if the probe was in the target set. On most
trials, an automatic sense of familiarity (either high or low) is
thought to be sufficient to perform this task accurately and quickly
(e.g., Atkinson & Juola, 1973; Jonides, Marshuetz, Smith, Reuter-
Lorenz, & Koeppe, 2000). However, sometimes the probe is not a
current target, but it was a target on the very previous trial (i.e., a
recent negative trial). Reaction times (RTs) are slower for recent
negative trials, presumably because recent negative trial probes are
associated with an automatic sense of familiarity that usually
suggests that the probe is a target. On recent negative trials,
Work on this article was supported by National Institute of Mental
Health Grant MH072706. I thank the patients and staff at Fulton State
Hospital, Fulton, Missouri, and at United Behavioral Health Services,
Columbia, Missouri, for their kind assistance with this research. I also
thank Kamila Cass, Angela Cain, and Aaron Thompson for all of their help
with this research.
Correspondence concerning this article should be addressed to John G.
Kerns, Department of Psychological Sciences, University of Missouri, 214
McAlester Hall, Columbia, MO 65211. E-mail: kernsj@missouri.edu
Journal of Abnormal Psychology Copyright 2007 by the American Psychological Association
2007, Vol. 116, No. 2, 279–289 0021-843X/07/$12.00 DOI: 10.1037/0021-843X.116.2.279
279
controlled recollection processes are thought to be engaged to
recover specific source information to accurately decide that the
probe was not in the current target set (e.g., Clark & Gronlund,
1996; McElree, Dolan, & Jacoby, 1999; Monsell, 1978). For
example, McElree and Dosher (1989) examined information accrual
over time and found evidence for two processes in memory
performance, a fast process sensitive to item familiarity and a
slower process sensitive to source information. In addition to
recognition memory tasks, in semantic processing tasks, controlled
retrieval is also thought to be involved in retrieving semantic
information when strong automatic associations between concepts
are absent (Wagner, Pare-Blagoev, Clark, & Poldrack, 2001).
The current research examined whether two communication
impairments in schizophrenia, FTD and poverty of speech, were
differentially associated with working memory and controlled retrieval.
Some previous research suggests that working memory
deficits might be associated with FTD. For example, in a previous
schizophrenia study, poor performance on the N-Back task was
associated with increased FTD (Kerns & Berenbaum, 2003). Similarly,
disorganization symptoms, which include FTD, have also
been associated with poor working memory performance (Cohen,
Barch, Carter, & Servan-Schreiber, 1999). Language production
involves maintaining a speech topic during ongoing speech and
also monitoring speech output for communication effectiveness
(Levelt, 1989). FTD in schizophrenia might reflect poor working
memory, which results in problems maintaining a speech topic and
remaining on track during speech (Barch & Berenbaum, 1997). In
addition, poor working memory might contribute to problems in
monitoring what has been said and what still needs to be said in
order to convey a particular idea (Kerns & Berenbaum, 2003;
Petrides, 1995). In contrast to FTD, there has not been consistent
evidence that poverty of speech is associated with poor working
memory (e.g., Cohen et al., 1999; Kerns & Berenbaum, 2003).
Although poverty of speech has not been consistently associated
with working memory, some previous research suggests that poverty
of speech might be associated with poor controlled retrieval.
For example, one brain region that has been consistently associated
with controlled retrieval is the left ventrolateral cortex, particularly
Brodmann’s area (BA) 45 (Jonides et al., 1998; Wagner et al.,
2001). There is evidence that damage to left ventrolateral prefrontal
cortex (PFC) can reduce speech output. For example, one
patient with a tumor in left BA 45 exhibited a marked reduction in
her speech (Robinson, Blair, & Cipolotti, 1998). Interestingly, this
patient exhibited reduced speech output primarily when controlled
retrieval demands seemed high. For example, she could produce a
normal amount of speech when strong associations existed between
concepts (i.e., familiar and well-learned information) or
when a high amount of contextual information was provided to
guide speech (e.g., describe what is happening in a picture). In
contrast, her speech output was markedly reduced in the absence of
strongly associated information or when little contextual information
was provided to guide speech (e.g., needing to describe what
would happen next in a picture). This suggests that poverty of
speech in people with schizophrenia could also be associated with
poor controlled retrieval. An initial stage in language production is
message generation and speech planning (Barch & Berenbaum,
1997; Levelt, 1989). Perhaps speech output is reduced in people
with poverty of speech because of poor controlled retrieval of
lexical–semantic representations, which could disrupt message
generation and speech planning. Some previous research on poverty
of speech in schizophrenia seems consistent with the hypothesis
that poverty of speech might be associated with poor controlled
retrieval. For example, poverty of speech is associated with
decreased verbal fluency (e.g., Stolar, Berenbaum, Banich, &
Barch, 1994), and successful fluency performance has been associated
with controlled memory retrieval (Rosen & Engle, 1997). In
addition, poverty of speech in schizophrenia has been found to
increase when less contextual information is provided to speakers
(Barch & Berenbaum, 1997). However, previous research has not
directly examined whether poverty of speech in schizophrenia is
associated with controlled retrieval task performance.
Although some previous research suggests that poverty of
speech could be associated with poor controlled retrieval, in contrast
one previous schizophrenia study found that FTD did not
have a significant zero-order association with controlled retrieval
(Kerns & Berenbaum, 2003). However, in that patient study,
controlled retrieval did interact with working memory to predict
FTD, with the highest amount of FTD associated with both poor
controlled retrieval and poor working memory. Hence, although by
itself controlled retrieval may not be associated with increased
FTD, poor controlled retrieval might be associated with increased
FTD only in people who also have poor working memory. As
previously discussed, problems with controlled retrieval might be
associated with difficulty in retrieving speech topics and retrieving
specific lexical–semantic representations, resulting in less fluent
and less effective speech (e.g., being unable to say what might
happen next in a picture; Robinson et al., 1998). Hence, poor
controlled retrieval might be associated with reduced communication
effectiveness, such as not retrieving situationally appropriate
speech topics and not being able to retrieve specific lexical–
semantic representations to clearly convey a particular idea. At the
same time, working memory is associated with the ability to
monitor ongoing behavior (Petrides, 1995). Hence, poor working
memory might be associated with reduced monitoring of communication
effectiveness. Therefore, the combination of both reduced
communication effectiveness (poor controlled retrieval) and reduced
monitoring of communication effectiveness (poor working
memory) might be associated with elevated FTD (decreased
speech clarity). However, potentially, with poor controlled retrieval
but intact working memory, there is a decrease in speech
amount but not an increase in speech disorganization due to an
intact ability to monitor ongoing speech for instances of reduced
clarity. Hence, controlled retrieval and working memory might
interact to predict FTD. However, there were several limitations of
that previous patient study that found an interaction between
working memory and controlled retrieval predicting FTD (Kerns
& Berenbaum, 2003). For example, sample size was relatively
small, only a single controlled retrieval task was examined, and a
task psychometrically matched to the controlled retrieval task was
not used. The current study examined whether poor performance
on multiple controlled retrieval tasks, but not psychometrically
matched tasks, would interact with poor working memory to
predict increased FTD.
Overall, the current research examined whether FTD and poverty
of speech were associated with distinct cognitive control
components. In this study, people with schizophrenia and control
participants completed multiple working memory and controlled
retrieval tasks. This research examined whether (a) FTD was
280 KERNS
associated with poor working memory, (b) poverty of speech was
associated with poor controlled retrieval, and (c) working memory
and controlled retrieval interacted to predict FTD.
Method
Participants
Participants were 47 people who met Diagnostic and Statistical
Manual of Mental Disorders (4th ed.; DSM–IV; American Psychiatric
Association, 1994) criteria for schizophrenia-spectrum disorders
(schizophrenia, n
34; schizoaffective, n
12; delusional
disorder, n
1). Participants either were clinically stable inpatients
(n
39) at a psychiatric hospital (with a largely forensic
population) or were clinically stable outpatients (n
8) living in
central Missouri. Participant demographic information is presented
in Table 1. Diagnoses were based on the psychotic, mood, and
substance-use disorders sections of the Structured Clinical Interview
for the DSM–IV (SCID; First, Spitzer, Gibbon, & Williams,
1998) and a review of clinical records. No participants met criteria
for a current substance-use diagnosis, and no participant had
undergone drug detoxification in at least the past 6 months. Except
for 1 person who had refused all medication, all participants were
taking antipsychotic medication at the time of their participation.
Chlorpromazine unit equivalents (Bezchlibnyk-Butler & Jeffries,
2004; Blanchard & Neale, 1992) were not associated with FTD
(r
.01), and including it as a covariate did not change any study
results (but see Blanchard & Neale, 1992, for problems in ruling
out medication effects). Symptoms were measured using the Brief
Psychiatric Rating Scale (Overall & Gorham, 1962) and the Scale
for the Assessment of Negative Symptoms (Andreasen, 1982).
To examine whether people with schizophrenia were impaired
in their cognitive control task performance, I compared their
performance with that of a nonpsychiatric control group. There
were 30 control participants recruited via flyers in central Missouri.
Control participants did not report a history of psychosis,
and all were not currently receiving any psychiatric or psychological
treatment. They did not differ significantly ( ps  .25) from
participants with schizophrenia in age (mean age in control participants

39.4, SD
9.1), paternal education (in control participants,
years of paternal education
12.3, SD
3.2; in patients,
years of paternal education
11.8, SD
3.2), race/ethnicity (in
control participants, percentage African American
25%), or
gender (in control participants, percentage male
70). Control
participants did have significantly more years of education than
patients (mean years of education in control participants
15.2,
SD
1.7).
Measures
Verbal communication impairments. Participants with schizophrenia
(but not control participants) completed an approximately
5 to 20 min structured interview, which was audiotaped and
transcribed. The interview consisted of 18 questions regarding
interests and general personal information (e.g., “What kinds of
movies do you like?” “Can you describe where you live now?”),
and has been used in previous FTD research (Kerns & Berenbaum,
2003). The measure of poverty of speech was the total number of
words a participant spoke. To measure FTD, six research assistants
rated the typed transcripts using the Communication Disturbances
Index (CDI; Docherty, 1996; Docherty, DeRosa, & Andreasen,
1996). The CDI rates the number of speech unclarities, with an
unclarity being any speech passage in which the meaning is
sufficiently unclear to impair the overall meaning of the speech
passage. The CDI was developed as an extension of a previous
measure of unclear referents in speech that has been used frequently
in previous schizophrenia research (Rochester & Martin,
1979). The CDI itself has now been used frequently in schizophrenia
research as a measure of disorganized and disordered speech
(e.g., Docherty, 2005; Kerns & Berenbaum, 2003). It is strongly
Table 1
Demographic and Clinical Data for Participants With Schizophrenia (n
47)
Variable % M SD Range
Gender (% male) 81
Race/ethnicity (% African American) 26
Age (years) 40.1 8.9 22–56
Education (years) 12.0 2.0 7–18
Mini-Mental State Examination (out of 30) 28.2 1.8 23–30
Medication
Chlorpromazine equivalents 429.7 534.2 0–2,742
% taking antipsychotics 98
% taking mood stabilizers 49
% taking antidepressants 43
% taking anticholinergics 40
Verbal communication impairments
FTD (unclarities per 100 words) 0.70 0.69 0–2.56
Alogia (no. of words) 968.4 1,111.7 115–4,954
Other symptoms
Delusions (BPRS: possible 1–7) 3.5 1.7 1–7
Hallucinations (BPRS: possible 1–7) 2.2 1.6 1–7
Flat affect (SANS: possible 0–5) 2.4 1.4 0–5
Avolition (SANS: possible 0–5) 1.6 1.4 0–5
Note. FTD
formal thought disorder; BPRS
Brief Psychiatric Rating Scale; SANS
Scale for the
Assessment of Negative Symptoms.
COMMUNICATION IMPAIRMENTS AND COGNITIVE CONTROL 281
associated with older measures of FTD such as the Thought,
Language, and Communication (TLC) scale (Docherty et al.,
1996) and has also been found to detect speech disorder in firstdegree
relatives of people with schizophrenia (e.g., Docherty,
Gordinier, Hall, & Dombrowski, 2004). Of importance, the CDI is
a more sensitive measure of speech disorder than the TLC, potentially
making it useful for research examining associations between
FTD and cognitive task performance.
Working memory tasks. Participants completed two different
working memory tasks: the N-Back and the Sternberg Probe Item
Recognition task. On the N-Back (Cohen et al., 1997), participants
saw a series of single letters on a computer screen. For every letter,
participants decided whether it was the same or a different from
the letter two letters previously. Each letter was preceded by a
fixation cross for 0.5 s. Each letter then appeared for 2 s and was
followed by a blank screen for 2.5 s. Participants completed four
blocks of 20 trials each. On half of the trials, the current letter was
different from the letter two letters previously (i.e., negative trials).
On half of these negative trials, the current letter was the same as
the letter either one or three letters previously (i.e., “distraction
trials”). The inclusion of distraction trials ensures that to do the
task well, participants actually had to maintain items in working
memory rather than being able to rely on a more passive recognition
strategy to perform the task (Gray, Chabris, & Braver, 2003).
The dependent variable for the N-Back task was d’, calculated as
the z score for hit rate minus the z score for the false-alarm rate
(Macmillan & Creelman, 1991). Of importance, previous research
has found that FTD is not associated with a task psychometrically
matched to the N-Back (Kerns & Berenbaum, 2003). Therefore, to
allow more time for additional tasks, a task psychometrically
matched to the N-Back was not included.
The second working memory task was the Sternberg Probe Item
Recognition task (Jonides et al., 1998). On each trial participants
saw a target set of three letters arranged around a central fixation
cross for 3 s. Then, after a 2-s delay, participants saw a single
probe letter, and they needed to decide whether the probe letter
was in the target set they had just seen. Participants had 3.5 s to
respond to the probe. Participants completed five blocks of 24
trials each. The dependent variable was accuracy rate.
Controlled retrieval tasks. In addition to providing a measure
of working memory, the Sternberg Probe Item Recognition task
also provides a measure of controlled retrieval (Jonides et al.,
1998). On half of all Sternberg trials, the probe letter was not in the
target set (i.e., negative trials). On half of the negative trials, the
probe letter was not in the target set but was in the target set of the
very previous trial (i.e., recent negative trials). As in previous
research (Jonides et al., 1998), the dependent variable was the RT
(note that all RT measures in this study involve only correct trials)
difference for recent negative trials minus the RT for nonrecent
negative trials (i.e., the Sternberg controlled retrieval score). As
previously discussed, recent negative trials are thought to involve
controlled recollection of source information to overcome the
automatic sense of familiarity from having been a recently presented
item (e.g., McElree et al., 1999; McElree & Dosher, 1989).
In addition to the Sternberg task, the second controlled retrieval
task was the Semantic Comparison Task (Wagner et al., 2001). On
this task, participants saw a single probe word above a fixation
cross and two words below it. Participants decided which word at
the bottom was semantically related to the probe word at the top.
Participants had 4.5 s to respond. There were two different trial
types. On strong trials, the semantically related words were
strongly associated with each other (e.g., curfew–late, oatmeal–
breakfast, whisker–beard). On weak trials, the semantically related
words were weakly associated with each other (e.g., curfew–cop,
oatmeal–morning, whisker–chin). Words were chosen from published
norms for word associations (Postman & Keppel, 1970). For
each probe word (displayed at the top of the screen), one strong
associate and one weak associate were selected. The strong and
weak associates were significantly different from each other in
association strength, .23 versus less than .01, t(91)
15.24, p 
.01 (with association strength meaning proportion of people out of
100 who gave the word as an associate of the probe; e.g., for the
probe word health, 250 out of 1,000 gave the word sickness; in
contrast, only 2 out of 1,000 gave the word strength). If amount of
semantic priming (at short stimulus onset asynchronies) is taken as
a measure of automatic spreading activation (Neely, 1991), then
strong trials should reflect automatic spreading activation to a
much greater extent than weak trials (note that the Semantic
Comparison Task is effectively a short stimulus onset asynchrony
design). This is because association strength is a very strong
predictor of semantic priming (Shelton & Martin, 1992). In contrast,
words that are semantically related but not associatively
related have often been found not to result in significant semantic
priming (Shelton & Martin, 1992; note that semantic priming for
unassociated but semantically related words has been found, but
sharing a high number of semantic features may be a critical
variable; e.g., duck and cow are semantically related, but they do
not share many semantic features; Cree & McRae, 2000; McRae,
de Sa, & Seidenberg, 1997). Hence, on strong trials, which involve
highly associated word pairs, the amount of automatic spreading
activation should be relatively high. Therefore, on strong trials,
automatic retrieval of semantic information from memory should
make a relatively large contribution to semantic comparison decisions
(i.e., deciding which word is related to the probe; Wagner et
al., 2001). In contrast, on weak trials, which involve unassociated
word pairs, amount of automatic spreading activation should be
small. Therefore, on weak trials, automatic retrieval of semantic
information is thought to be generally insufficient for the retrieval
of adequate semantic information to make semantic comparison
decisions (Wagner et al., 2001). Hence, on weak trials, controlled
retrieval processes are thought to be engaged in order to retrieve
sufficient semantic information (Wagner et al., 2001). Wagner et
al. found that weak trials activated the left ventrolateral PFC more
than did strong trials (Wagner et al., 2001; note that the specific
left ventrolateral PFC region activated has been strongly associated
with controlled semantic processing in previous research; e.g.,
Poldrack et al., 1999). Moreover, in the Wagner et al. study, the
same left ventrolateral PFC region activated on weak trials was
more strongly activated by another manipulation also thought to
increase semantic retrieval demands (having to retrieve four rather
than only two words; Wagner et al., 2001). On the Semantic
Comparison Task, participants saw each probe word with one of its
randomly selected semantic associates. Distractor words that were
not semantically associated were selected to be equal in word
length and frequency to the semantically related words (Francis &
Kucera, 1982). Participants completed four blocks of 20 trials each
(half of the trials were strong trials, and half were weak). The
282 KERNS
dependent variable was the RT for weak trials minus the RT for
strong trials (i.e., the semantic controlled retrieval score).
Psychometric control tasks. Participants also completed a task
psychometrically matched to the Sternberg controlled retrieval
score, the letter search task. On this task, participants saw a single
letter in the top half of the screen above a fixation cross and either
two or four letters below the fixation cross. Participants decided if
the single letter at the top was one of the letters at the bottom.
Participants had 3.5 s to respond. Participants completed four
blocks of 24 trials each. The dependent variable was the RT for
four-letter trials minus the RT for two-letter trials (i.e., the letter
search RT score, with, on average, longer RTs to search through
four letters than to search through two letters).
In addition, to examine whether associations between symptoms
and the semantic controlled retrieval score could be due to generalized
poor task performance, a psychometrically matched semantic
RT baseline score was calculated by taking the difference in RT
between strong trials on the Semantic Comparison Task and twoletter
trials on the letter search task. There are several similarities
between two-letter trials on the letter search task and strong trials
on the Semantic Comparison Task. They both involve comparing
a single probe at the top of the screen with two possibly related
items at the bottom of the screen. However, only the semantic task
involves processing words. Hence, if people have a generalized
verbal impairment, it might be evident in a larger difference in RT
for strong Semantic Comparison trials minus two-letter trials on
the letter search task (i.e., the semantic RT baseline score). Of
interest, the semantic RT baseline score was strongly associated
with decreased education (r
–.42, p  .01), suggesting that poor
verbal processing was associated with less education.
Procedure and Data Analysis
Participants completed the study in the following order: Mini-
Mental State Examination (Folstein, Folstein, & McHugh, 1975),
letter search, Sternberg Probe Item Recognition, Structured Clinical
Interview for the DSM–IV, structured speech interview, Semantic
Comparison Task, and the N-Back. In the analysis of RTs,
only correct trials were used. In addition, all trials on which RT
was less than 200 ms were removed as a minimum RT cutoff.
However, a maximum RT cutoff was not used in this research for
two reasons. First, each speeded-response task in this study already
involved a certain maximum allowable RT (e.g., for the Sternberg
task, it was 3.5 s). Second, analysis of RTs on a different cognitive
task (the Implicit Association Test; Greenwald, Nosek, & Banaji,
2003) has shown that inclusion of long RT trials (i.e.,  3 s) results
in even more valid results than their exclusion (i.e., even stronger
associations with theoretically relevant measures). However, a
problem with the inclusion of long RT trials is their disproportionate
influence on measures of central tendency. To correct for this,
following Greenwald et al. (2003), I first log transformed raw RT
data to reduce the impact of long RTs on mean scores. Hence, in
this study, all reported RT analyses involved the use of logtransformed
scores. Nevertheless, use of non-log-transformed data
resulted in virtually identical results. Following Kramer, Humphrey,
Larish, Logan, and Strayer (1994), reliability was calculated
by calculating two measures of each variable for each participant
by using odd and even numbered trials, calculating the correlation
across participants, and then correcting it using the Spearman–
Brown formula.
Results
CDI Ratings
Interrater reliability for the total CDI score, measured using an
intraclass correlation (Shrout & Fleiss, 1979), treating the raters as
random effects and the mean of the six raters as the unit of
reliability, was .94. Following Docherty and colleagues (Docherty,
2005; Docherty et al., 1996), raw CDI scores were corrected for
total amount of speech; hence, reported CDI scores in Table 1 are
the number of speech unclarities per 100 words of speech. This
means that, on average, in this study participants had an unclarity
every 140 words and the maximum rate of FTD in this study was
an unclarity every 40 words; to illustrate, note that this sentence
includes 40 words. The mean CDI score in the current study (.70)
is very similar to the mean CDI score in an earlier schizophrenia
study (.64) that used the same interview (Kerns & Berenbaum,
2003; with both of these studies finding robust associations between
cognitive performance and CDI scores, suggesting they did
not suffer from decreased sensitivity or truncated range). FTD
scores vary by speech contexts, with interviews about more complex
and less commonplace topics producing higher average levels
of FTD (Barch & Berenbaum, 1997; Johnston & Holzman, 1979;
Kerns & Berenbaum, 2003). The current study involved a structured
interview with 18 relatively simple questions regarding fairly
commonplace personal information (e.g., “What is your favorite
color?”, “How come?”, “Could you describe where you live
now?”, “Could you describe your favorite person in the world?”).
Hence, it would be expected that average CDI scores would be
lower in the current study than in studies that involved more
complex speech topics (e.g., discussing religious and political
beliefs; Docherty et al., 1996).
Cognitive Task Performance Correlations
As can be seen in Table 2, consistent with previous research
(Kerns & Berenbaum, 2003), overall accuracy on the Sternberg
task was associated with N-Back performance in both patients and
control participants. Hence, a single working memory task performance
variable was created by summing together N-Back and
Sternberg accuracy z scores. In addition, as can be seen in Table 2,
as expected, Sternberg controlled retrieval score was associated
with semantic controlled retrieval score in both patients and control
participants. Hence, a single controlled retrieval task performance
variable was created by summing together Sternberg controlled
retrieval and semantic controlled retrieval z scores.
Moreover, psychometric control tasks were not significantly associated
with any other task. At the same time, consistent with
previous research (Kerns & Berenbaum, 2003), working memory
and controlled retrieval tasks were not significantly associated
with each other. However, it is also possible that performance on
N-Back distraction trials (current letter same as letter one back or
three back) might be thought to involve controlled retrieval. Consistent
with this, there was some evidence that performance on
N-Back distraction trials was associated with controlled retrieval
performance in control participants (r
.37, p  .05), but not in
COMMUNICATION IMPAIRMENTS AND COGNITIVE CONTROL 283
people with schizophrenia (r
.10). Speculatively, perhaps poor
working memory performance (i.e., poorer updating and maintenance
of targets) in people with schizophrenia limited the association
between performance on N-Back distraction trials and controlled
retrieval tasks.
Cognitive Task Performance in People With
Schizophrenia and Control Participants
As can be seen in Table 3, people with schizophrenia exhibited
significantly poorer working memory performance than control
participants, t(75)
5.35, p  .01, effect size r
.53. In addition,
people with schizophrenia also exhibited significantly poorer performance
(i.e., greater RT slowing) on controlled retrieval tasks
than did control participants, t(75)
2.21, p  .05, r
.25. People
with schizophrenia also exhibited significantly poorer performance
on the letter search psychometric control task, t(75)
3.28, p 
.01, r
.35, but not on the semantic baseline control measure,
t(75)
0.16, p  .85, r
.02 (people with schizophrenia were
also less accurate on the Semantic Comparison Task: schizophrenia
mean for strong trials
.94, SD
.09, Mdn
.97; for weak
trials M
.90, SD
.11, Mdn
.94; control mean for strong
trials
.98, SD
.02, Mdn
.97; for weak trials M
.96, SD

.03, Mdn
.97; group differences ps  .05).
In addition, as can be seen in Table 3, the letter search RT score
had slightly greater true-score variance (the reliable part of observed
variance, or Reliability  Variance) than the Sternberg
controlled retrieval score. In addition, the difference between four
versus two letters on the letter search task is actually larger (i.e.,
appeared to be a more difficult task) than the difference between
recent versus nonrecent negative trials on the Sternberg task. In
addition, the mean semantic RT baseline score was larger (i.e.,
appeared to be a more difficult task) and had greater true-score
variance (i.e., Reliability  Variance) than the semantic controlled
retrieval score. Hence, if poverty of speech is associated with the
semantic controlled retrieval score but not with the semantic RT
baseline score, then the association with semantic controlled retrieval
score is most likely not due to a generalized performance
deficit.
Verbal Communication Impairments and Cognitive
Control Task Performance
As can be seen in Table 4, only FTD, not poverty of speech, was
associated with poor working memory. In contrast, only poverty of
speech, not FTD, was associated with poor controlled retrieval.
Next examined was whether the correlations between FTD and
poverty of speech with cognitive control components were significantly
different from each other (Meng, Rosenthal, & Rubin,
1992). Working memory was significantly more strongly associated
with FTD than with poverty of speech (Z
2.15, p  .05). In
contrast, controlled retrieval was significantly more strongly asso-
Table 2
Correlations Between Cognitive Tasks in Participants With Schizophrenia and Control Participants
Variable 1 2 3 4 5 6
Working memory
1. N-Back — .46*** .21 .11 .18 .17
2. Sternberg accuracy .39*** — .16 .04 .08 .11
Controlled retrieval
3. Sternberg controlled retrieval .07 .11 — .35* .09 .06
4. Semantic controlled retrieval .04 .12 .43*** — .08 .04
Psychometric control tasks
5. Letter search RT .10 .23 .19 .01 — .19
6. Semantic RT baseline score .03 .08 .08 .21 .18 —
Note. Values below the diagonal are for participants with schizophrenia; values above the diagonal are for control participants. RT
reaction time.
* p
.054. *** p  .01.
Table 3
Cognitive Task Performance
Measure (reliability)
Schizophrenia Control
True-score
M SD M SD variance
Working memory tasks
N-Back d (.68) 1.12 0.70 2.92 1.18 1.01
Sternberg accuracy rate (.74) 0.91 0.12 0.97 0.02 0.003
Controlled retrieval tasks
Sternberg controlled retrieval (.54) 69.6 124.2 53.2 54.7 7,150.2
Semantic controlled retrieval (.52) 216.7 153.8 176.0 124.7 10,769.9
Psychometric control tasks
Letter search RT (.58) 286.6 145.8 182.3 50.9 10,458.4
Semantic RT baseline score (.54) 663.8 421.7 653.0 283.1 77,946.7
Note. RT
reaction time.
284 KERNS
ciated with poverty of speech than with FTD (Z
2.60, p  .01).
In addition, as can be seen in Table 4, although poverty of speech
was associated with controlled retrieval, it was not associated with
performance on control tasks psychometrically matched to the
controlled retrieval tasks. Moreover, although working memory
and controlled retrieval measures had significant zero-order associations
with FTD and poverty of speech, respectively, these
cognitive measures were not associated with positive symptoms
(rs  .20).
Interaction Between Working Memory and Controlled
Retrieval Predicting FTD
Next examined was whether working memory and controlled
retrieval interacted to predict FTD. As can be seen in Table 5, in
a hierarchical multiple regression analysis, the interaction between
working memory and controlled retrieval significantly predicted
FTD. As can be seen in Figure 1, the highest levels of FTD were
associated with both poor working memory and poor controlled
retrieval. In contrast, working memory did not interact with either
of the psychometric control tasks to predict FTD ( ps  .70). In
addition, the interaction between working memory and controlled
retrieval did not predict either poverty of speech or positive symptoms
(all ps  .40; at the same time, the lack of zero-order
association between controlled retrieval and FTD reported in Table
4 and the significant association between working memory and
FTD even with controlled retrieval in the regression analysis
reported in Table 5 suggest that controlled retrieval does not
mediate the association between working memory and FTD; Baron
& Kenny, 1986; MacKinnon, Lockwood, Hoffman, West, &
Sheets, 2002).
Discussion
This study suggests that in schizophrenia, the verbal communication
impairments FTD and poverty of speech might be differentially
associated with deficits in distinct cognitive control components.
In this study, FTD, but not poverty of speech, was
associated with poor working memory. In contrast, poverty of
speech, but not FTD, was associated with poor controlled retrieval.
This suggests that by itself, poor controlled retrieval is associated
only with poverty of speech and not with FTD. However, at the
same time, FTD was predicted by an interaction between working
memory and controlled retrieval. Hence, consistent with an earlier
study (Kerns & Berenbaum, 2003), it appears that the highest
levels of FTD are associated with both poor working memory and
poor controlled retrieval.
In this study, FTD was strongly associated with poor working
memory task performance. The current results for FTD and working
memory appear to be generally consistent with previous research
finding associations between FTD and poor working memory
(Cohen et al., 1999; Kerns & Berenbaum, 2002, 2003).
Moreover, in a previous analogue study, manipulations of working
memory demands were found to increase FTD (Kerns & Berenbaum,
2003). However, at the same time, a couple of studies have
not reported a significant association between working memory
and FTD. For example, one study found that FTD was not significantly
associated with performance on the letter–number sequence
task (Goldberg et al., 1998). However, in addition to
having a relatively small sample size (n
23), in assessing FTD
that study used global scores from the TLC (Andreasen, 1979a),
which includes a number of negative thought disorder items including
poverty of speech. Hence, it is unclear from that study
whether FTD was not associated with poor working memory. In
addition, one study found that FTD was not significantly associated
with performance on the reading span working memory task
(Bagner, Melinder, & Barch, 2003). However, in another recent
study with nearly double the sample size, FTD was found to be
strongly associated with poor reading span performance (Berenbaum,
Kerns, Vernon, & Gomez, 2006). Hence, on the whole it
appears that FTD in people with schizophrenia tends to be associated
with poor working memory task performance. Thus, disorganized
speech might reflect problems in maintaining a particular
speech topic and remaining on track during speech (Barch &
Berenbaum, 1997). In addition, poor working memory might contribute
to problems in monitoring communication effectiveness
(Petrides, 1995), for example, monitoring what has been said and
what still needs to be said in order to clearly convey a particular
idea (Levelt, 1989).
In contrast to FTD, in this study poverty of speech was not
associated with poor working memory. The current results for
poverty of speech and working memory also appear to be generally
consistent with previous research (Cohen et al., 1999; Kerns &
Berenbaum, 2003). However, one previous study did find a sig-
Table 4
Correlations Between Cognitive Tasks and Verbal
Communication Impairments
Cognitive measure FTD
Poverty of
speech
Cognitive control components
Working memory .51*** .12
Controlled retrieval .01 .46***
Psychometric control tasks
Letter search RT score .06 .06
Semantic RT baseline score .11 .08
Note. Note that higher poverty of speech scores indicate a lesser amount
of speech; also, higher controlled retrieval scores indicate better performance
(i.e., less RT slowing). FTD
formal thought disorder; RT

reaction time.
*** p  .01.
Table 5
Hierarchical Multiple Regression With Working Memory and
Controlled Retrieval Predicting Formal Thought Disorder
Predictor B SEB 
Step 1
Working memory 0.62 0.16 .52***
Controlled retrieval 0.01 0.11 .01
Step 2
Working memory 0.57 0.16 .48***
Controlled retrieval 0.04 0.11 .05
Working Memory  Controlled Retrieval 0.44 0.21 .29**
Note. R2 for Step 1
.28; R2 for Step 2
.08 ( p  .05).
** p  .05. *** p  .01.
COMMUNICATION IMPAIRMENTS AND COGNITIVE CONTROL 285
nificant association between poverty of speech and performance
on a working memory task, the speaking span task (Melinder &
Barch, 2003). However, the speaking span task involves language
production, as participants must produce sentences while maintaining
words in working memory. Given that poverty of speech is
associated with decreased language production, it is possible that
language production ability could account for the association between
poverty of speech and speaking span performance. At the
same time, that same study found that poverty of speech was not
significantly associated with another working memory task
(Melinder & Barch, 2003). In addition, another recent study found
that poverty of speech was virtually unassociated with performance
on working memory tasks (reading span and A-X CPT;
Berenbaum et al., 2006). Hence, on the whole it appears that
poverty of speech in people with schizophrenia tends not to be
associated with poor working memory task performance.
Although poverty of speech may not be associated with poor
working memory, the current study did find that poverty of speech
may be associated with another aspect of cognitive control, poor
controlled retrieval. Although previous research has not directly
examined the relationship between poverty of speech and controlled
retrieval, the current results for poverty of speech and
controlled retrieval appear to be generally consistent with previous
research on poverty of speech. For example, poverty of speech has
been consistently associated with poor verbal fluency (Joyce,
Collinson, & Crichton, 1996; Stolar et al., 1994). One aspect of
successful fluency performance is to retrieve new words in the face
of competition from previously spoken words (Rosen & Engle,
1997). Hence, problems in controlled retrieval could contribute to
problems in verbal fluency. Similarly, poverty of speech has been
associated with an increased disorganization of semantic clusters
in a semantic fluency task (Sumiyoshi et al., 2005), which might be
due to difficulty in retrieving items from one category after having
already retrieved some items from that category. Another result
that seems generally consistent with the association between controlled
retrieval and poverty of speech is that poverty of speech has
been found to increase when less prior context information has
been provided (Barch & Berenbaum, 1997). Providing more context
information could ease controlled retrieval demands as more
context information could provide a stronger memory cue for the
retrieval and selection of information from memory (Miller &
Cohen, 2001; Robinson et al., 1998). In other schizophrenia research,
poverty of speech has been found to be associated with
increased between-clauses pauses (Alpert, Clark, & Pouget, 1994).
This also seems generally consistent with a controlled retrieval
deficit, as between-clauses pauses presumably reflect relative difficulty
of retrieving new content for ongoing speech. Hence, a
number of previous studies on poverty of speech seem generally
consistent with poverty of speech being associated with a deficit in
controlled retrieval. Thus, decreased speech output in poverty of
speech might in part reflect problems in retrieving lexical–
semantic representations that disrupt the ability to generate a
speech message and to plan upcoming speech (Barch & Berenbaum,
1997; Levelt, 1989).
In contrast to the association between controlled retrieval and
poverty of speech, by itself controlled retrieval was not associated
with FTD. However, the current study suggests that controlled
retrieval deficits might be associated with increased FTD only in
some people with schizophrenia. In particular, poor controlled
retrieval was associated with the highest levels of FTD in those
people who also had poor working memory. In fact, as can be seen
in Figure 1, the current results suggest that controlled retrieval
might be an important factor in predicting FTD, as in people with
good controlled retrieval working memory was a much weaker
predictor of FTD (i.e., controlled retrieval appears to moderate the
association between working memory and FTD; Baron & Kenny,
1986). An interaction between working memory and controlled
retrieval predicting FTD has been found in one previous schizophrenia
study and in one analogue FTD study (Kerns & Berenbaum,
2003). Hence, overall, it appears that the highest level of
FTD might be associated with deficits in both working memory
and controlled retrieval. Presumably, poor controlled retrieval
might be associated with reduced communication effectiveness, as
speakers might have difficulty retrieving (a) situationally appropriate
speech topics and (b) specific lexical–semantic representations
to clearly convey a particular idea (Robinson et al., 1998). At
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Good Poor
Poor
Good
CDI Score (unclarities per 100 words)
Controlled
Retrieval
Working Memory
Figure 1. Interaction of working memory and controlled retrieval task performance predicting formal thought
disorder. Scores are predicted values computed using unstandardized regression coefficients and 1 values; no
error bars are presented because these are predicted scores. CDI
Communication Disturbances Index.
286 KERNS
the same time, poor working memory might be associated with
problems in monitoring ongoing speech and monitoring communication
effectiveness (Petrides, 1995). Thus, the highest levels of
FTD might be associated with both reduced communication effectiveness
(poor controlled retrieval) and reduced monitoring of
communication effectiveness (poor working memory). However,
as has been found in previous research (Kerns & Berenbaum,
2003), in people who performed well on working memory tasks,
controlled retrieval was not associated with increased FTD; if
anything, it was associated with decreased FTD. One possibility is
that people with intact working memory are still able to effectively
monitor their speech. Hence, with good working memory but poor
controlled retrieval, people might reduce their speech output and
simplify their speech in order to maintain speech clarity. This is
similar to suggestions that some people with schizophrenia might
decrease the amount and complexity of their speech when they
recognize that they might have speech problems (Barch & Berenbaum,
1997). At the same time, it is also possible that people with
poor controlled retrieval might become more perseverative because
of problems in retrieving new information in the face of
competition from previously spoken information (Dell, Burger, &
Svec, 1997). For example, people with poor verbal fluency have
been found to perseverate on previously spoken items (Rosen &
Engle, 1997). Becoming more perseverative and repetitive while
still maintaining the ability to monitor speech might make speech
less creative but, perhaps, even clearer and easier to understand.
As previously discussed, one issue in research on verbal communication
impairments in schizophrenia is whether FTD and
poverty of speech reflect distinct or similar cognitive deficits
(Melinder & Barch, 2003). In particular, it has been suggested that
both FTD and poverty of speech might be associated with poor
cognitive control (e.g., Barch & Berenbaum, 1997). The current
study provides some evidence about how FTD and poverty of
speech might have different as well as similar relationships with
cognitive control components. One possible difference found in
this study is that poor working memory is only associated with
FTD. At the same time, the current study suggests that by itself
(i.e., in the absence of a working memory deficit) poor controlled
retrieval is only associated with poverty of speech. However, one
similarity found in this study is that controlled retrieval might play
a role in both FTD and poverty of speech, with FTD only being
related to poor controlled retrieval in the presence of working
memory deficits.
In the current study, people with schizophrenia performed more
poorly than control participants on both working memory and
controlled retrieval tasks. Previous research suggests that working
memory deficits in schizophrenia might not reflect a generalized
performance deficit (e.g., Cohen et al., 1999). However, from the
current results, it is not clear whether the overall poor performance
by people with schizophrenia on controlled retrieval tasks reflects
a specific controlled retrieval deficit or instead is due to a generalized
performance deficit. On the one hand, people with schizophrenia
did not differ from control participants on one of the
psychometric control measures, the semantic RT baseline score.
On the other hand, people with schizophrenia did differ from
control participants on the letter search RT score, with a seemingly
bigger difference on this task than on the controlled retrieval tasks.
Nevertheless, the psychometric control tasks were not associated
with poverty of speech and did not interact with poor working
memory to predict FTD. This suggests that associations between
poor controlled retrieval and communication impairments (i.e.,
poverty of speech and FTD) are likely not due to generalized poor
task performance.
One issue for future FTD research is to further explore the
nature of poor working memory in people with elevated FTD. One
possibility is that poor working memory might reflect a deficit in
controlled attention (i.e., capacity-limited attention), which some
working memory theorists have posited is a central component of
working memory storage and processing tasks (Cowan, 2005;
Engle, Tuholski, Laughlin, & Conway, 1999). A related issue for
future research might be to examine what brain regions are involved
in working memory deficits in people with high levels of
FTD. Dorsolateral PFC has been strongly associated with the
processing component of working memory (Barch, 2005). Potentially,
FTD reflects dorsolateral PFC disturbances in schizophrenia.
Consistent with this, disorganization symptoms have been
associated with decreased activity in the dorsolateral PFC (Mac-
Donald et al., 2005). At the same time, other brain regions are also
associated with working memory, such as the parietal cortex,
which appears to be involved in working memory storage and is
impaired in schizophrenia (Barch, 2005). Hence, FTD might be
associated with deficits in the PFC, in the parietal cortex, or
perhaps in the interaction between these two brain regions (Barch,
2005).
Another issue for future research is whether associations between
disorganized speech and cognitive control processes are
specific to schizophrenia or whether similar associations would be
found in other participants. There is some evidence that manipulations
of cognitive control processes can increase communication
disturbances in nonpsychiatric participants (Kerns & Berenbaum,
2003). This suggests that it is possible that similar associations
between cognitive control processes and disorganized speech
might be found in other participants (although levels of communication
disturbances would be expected to be much lower in other
groups).
One issue for future poverty of speech research is to further
examine whether poverty of speech is associated with problems in
controlled retrieval. As previously mentioned, both the Sternberg
task and the Semantic Comparison Task are thought to involve
controlled retrieval. For example, both tasks include a comparison
between trials that involve a relatively automatic memory mechanism
(sense of familiarity in Sternberg, spreading activation in
Semantic Comparison) versus trials that involve a more controlled
retrieval mechanism (recollection of specific source information in
Sternberg, controlled activation of unassociated semantic information
in Semantic Comparison). However, it is possible that these
tasks also share some other feature in common other than controlled
retrieval (e.g., strategy application and decision making;
McElree et al., 1999), with this other shared feature accounting for
the association between these tasks and poverty of speech. Future
research could use other research methods designed to discriminate
automatic and controlled memory processes, such as the
process dissociation framework (Jacoby, 1991), to further examine
whether poverty of speech is associated with poor controlled
retrieval. In addition, given that previous research has strongly
associated left ventrolateral PFC with controlled retrieval (e.g.,
Jonides et al., 1998; Wagner et al., 2001), future research could
examine whether poverty of speech is associated with activity in
COMMUNICATION IMPAIRMENTS AND COGNITIVE CONTROL 287
the left ventrolateral PFC. One other issue for future research
would be to examine whether other negative language symptoms
such as reduced syntactic complexity (Barch & Berenbaum, 1997)
are also associated with poor controlled retrieval.
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