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Graduate Student Journal of Psychology                                                                            Copyright 2008 by the Department of Counseling & Clinical Psychology

2008, Vol. 10                                                                                                                        Teachers College, Columbia University                         ISSN 1088-4661

Executive Functioning in Schizophrenia:

The Contributions of Attention, Working Memory,

Processing Speed, and General Intelligence

Cale D. Palmer
University of Hawaii at Manoa

Elaine Heiby
University of Hawaii at Manoa

Daryl Fujii
           University of Hawaii at Manoa

Velma Kameoka
University of Hawaii at Manoa

The purpose of this study was to assess the degree to which executive functioning performance

may be associated with indices of attention, working memory, processing speed, and general in-

telligence in 45 individuals with schizophrenia from a multicultural sample. It was hypothesized

that relatively higher performances on measures of these cognitive processes would be positively

associated with higher executive functioning performance, as measured by the Wisconsin Card

Sorting Test (WCST). Contrary to expectations, results indicated that attention, working memory,

and processing speed did not significantly correlate with executive functioning performance.

However, Wechsler Adult Intelligence Scale, Third Edition (WAIS-III) Full-Scale IQ scores did

significantly correlate with WCST performance, suggesting that general intellectual deficits may

underlie executive functioning impairments in schizophrenia.

Schizophrenia is a psychotic disorder often character-

ized by delusions and hallucinations (American Psychiatric

Association, 2000). Schizophrenia may also be conceptu-

alized as a chronic neurocognitive disorder with varied

levels of functioning and symptom presentations, including

deficits in attention, memory, processing speed, and execu-

tive functioning. Such cognitive deficits appear to predate

clinical symptoms (Murray, 1994), remain relatively stable

after the onset of schizophrenia (Heaton et al., 2001; Hoff

et al., 1999; Rund, 1998), and remain stable regardless of

baseline and changes in clinical state (Heaton et al., 2001).

Deficits in cognitive functioning may be considered core

symptoms of schizophrenia (Weickert et al., 2000) and

have been associated with relapse and functional outcome

(Chen et al., 2005; Green, Kern, Braff, & Mintz, 2000;

Sergi, Kern, Mintz, & Green, 2005; Woonings, Appelo,

Kluiter, Slooff, & van den Bosch, 2002). In addition, func-

tional outcome may be more reliably related to cognitive

impairment than positive symptomatic variables (Axelrod,

Goldman, Tompkins, & Jiron, 1994).

One such cognitive deficit that has been widely studied

in individuals with schizophrenia is executive functioning,

a broad  term comprised  of several  components, including

Correspondence and reprint requests to Cale Palmer at Depart-

ment of Psychology, University of Hawaii at Manoa, 2430

Campus Rd., Honolulu, HI  96822.

E-mail: cale@hawaii.edu.

determining what one wants or needs, conceptualizing the

future realization of that want or need, identifying and or-

ganizing the steps and resources required to achieve the

goal, weighing alternatives and making choices, and the

translation of a plan into action via sequences of complex

behavior in an orderly fashion (Lezak, 1995). Executive

functioning has also been described as involving volition,

planning, purposive action, and self-monitoring of behavior

(Green et al., 2000; Lezak, 1995), which enable the per-

formance of complex and high-level tasks. Lezak (1995)

has characterized executive abilities as “those capacities

that enable a person to engage successfully in independent,

purposive, self-serving behavior” (p. 42). Maintaining or

shifting mental sets, establishing goals, and planning are

crucial aspects of executive functioning (Stuss & Benson,

1986) and can be measured by neuropsychological tests

specifically designed to assess executive functioning.

One of the most established and widely used measures

of executive functioning is the Wisconsin Card Sorting

Test (WCST; Berg, 1948; Grant & Berg, 1948; Heaton,

Chelune, Talley, Kay, & Curtiss, 1993), a complex task

designed to assess the ability to shift cognitive strategies in

response to changing environmental contingencies. The test

requires subjects to perceive and abstract relevant attributes

and ignore irrelevant ones, to engage in hypothesis genera-

tion and testing, and to abandon irrelevant hypotheses or

principles when necessary (King & Snow, 1981). Success-

ful WCST performance is thought to involve strategic

planning, organized searching, goal-oriented behavior,

modulation of impulsive responding, and the ability to use



EXECUTIVE FUNCTIONING IN SCHIZOPHRENIA

39

environmental feedback to shift cognitive sets (Spreen &

Strauss, 1998).

In individuals with schizophrenia, performances on the

WCST are often impaired relative to normal and psychiat-

ric controls (Beatty, Jocic, Monson, & Katzung, 1994;

Everett, Lavoie, Gagnon, & Gosselin, 2001; Ilonen et al.,

2000; Johnson-Selfridge & Zalewski, 2001; Metz, Johnson,

Pliskin, & Luchins, 1994; Reed, Harrow, Herbener, &

Martin, 2002), and some of the research seeking to explain

the WCST performance impairment associated with

schizophrenia has centered on correlations with intellectual

or cognitive abilities, such as attention and working mem-

ory, measured by tests commonly used in neuropsychologi-

cal batteries. Results from these studies, however, have

often been unclear or conflicting, and much remains to be

known about the specific cognitive processes involved in

WCST performance and what processes contribute to the

relatively impaired WCST performance associated with

schizophrenia.

Some researchers, for example, have suggested that

attention may underlie WCST performance (Perry, Potterat,

& Braff, 2001; Stratta, Mancini, Mattei, Casacchia, &

Rossi, 1994). Differences between individuals with schizo-

phrenia in an inpatient setting and controls on WCST per-

formance may be eliminated after controlling for attention

using analysis of covariance (Kenny & Meltzer, 1991), and

attention training may remediate WCST deficits (Lopez-

Luengo & Vazquez, 2003). Other studies, however, suggest

that attention may be insufficient in explaining WCST per-

formance or have found no significant correlation between

WCST performance and attention (Chen et al., 1997; Dela-

hunty, Morice, & Frost, 1993; Frost et al., 1991; Goldberg,

Weinberger, Berman, Pliskin, & Podd, 1987; Greve, In-

gram, & Bianchini, 1998). Similarly, while some studies

have found evidence of an association between working

memory and executive functioning in schizophrenia

(Glahn, Cannon, Gur, Ragland, & Gur, 2000; Gold, Car-

penter, Randolph, Goldberg, & Weinberger, 1997; Gooding

& Tallent, 2002; Morice & Delahunty, 1996; Stone, Gab-

rieli, Stebbins, & Sullivan, 1998), others have not (Bellack,

Mueser, Morrison, Tierney, & Podell, 1990; Goldman, Ax-

elrod, & Tompkins, 1992; Greve et al., 1998; Stratta et al.,

1997; Vollema, Geurtsen, & van Voorst, 1995). Thus,

while attention and working memory have yet to fully ex-

plain WCST performance impairments, many studies do

suggest some degree of impairment, and differences in

sample composition and instruments across studies likely

contribute to inconsistent findings. In addition, few studies

have directly assessed the association between attention

and executive functioning, and of those that have, many

studies relied on visual rather than auditory stimuli when

measuring attention. As individuals with schizophrenia

may be relatively more impaired on auditory measures of

attention (Borgaro et al., 2003; Mirsky, Yardley, Jones,

Walsh, & Kendler, 1995; Mussgay & Hertwig, 1990), a

more sensitive measure of impairment may yield more con-

sistent, significant results.

Research appears relatively more limited with regard

to assessing processing speed in schizophrenia and its po-

tential contribution to impaired WCST performance. Indi-

viduals with schizophrenia have been found to have im-

paired processing speed (Egeland et al., 2003; Hong et al.,

2002; Saccuzzo & Braff, 1981), and this impairment may

result in a disrupted flow of information as new stimuli

enter before other stimuli have transferred (Felsten & Was-

serman, 1980; Saccuzzo & Braff, 1981). This slowed proc-

essing speed may cause individuals with schizophrenia to

lose information before being able to use it (Brebion et al.,

2000; Hartman, Steketee, Silva, Lanning, & Andersson,

2003), and thus may contribute to impaired WCST per-

formance. However, this hypothetical association has yet to

be directly assessed.

Finally, it is also possible that WCST performance im-

pairments associated with schizophrenia may be due to

deficits in generalized intelligence (Laws, 1999). While

some argue that WCST performance may not be fully ac-

counted for by IQ scores (Elliott, McKenna, Robbins, &

Sahakian, 1995; Morice, 1990), many studies have demon-

strated significant associations between WCST and IQ

scores (Dieci et al., 1997; Gold et al., 1997; Goldberg, Kel-

soe, & Weinberger, 1988; Ilonen et al., 2000; Laws, 1999;

Seidman et al., 1991), as well as IQ estimates (Koren et al.,

1998; Sweeney, Kelip, Haas, Hill, & Weiden, 1991) in in-

dividuals with schizophrenia. One study reported that IQ

scores account for approximately 40% of the variance in

WCST performance (Gold et al., 1997).

Additional support for a possible association between

IQ and WCST performance has been found in several

studies that compared groups of individuals with different

levels of IQ or WCST performance impairment. For exam-

ple, in a study by Goldstein, Beers, and Shemansky (1996),

individuals with poor WCST performance had significantly

lower IQ subtest scores compared to those individuals that

did not exhibit WCST performance impairment. Weickert

et al. (2000), also found relatively impaired WCST per-

formance in individuals with schizophrenia with lower IQ

estimates. In the same study, a minority of patients with

schizophrenia demonstrated an average level IQ, and, to a

lesser degree, they too demonstrated some WCST perform-

ance impairment compared to normal controls (Weickert et

al., 2000). Similarly, Kremen, Seidman, Faraone, and Tsu-

ang (2001), found that based on WCST and Visual-Verbal

Test scores (Feldman & Drasgow, 1981), abstraction-

executive function was relatively more impaired in indi-

viduals with schizophrenia who had an estimated low-

average IQ compared to those with average IQ, although

both groups demonstrated impaired abstraction-executive

function compared to IQ-matched normal controls.

Finally, in a study by Dieci et al. (1997), WCST per-

formance was not able to better discriminate healthy con-

trols from individuals with schizophrenia when compared

to IQ scores, suggesting that WCST may not represent a

pronounced deficit separate from a general intellectual

deficit. Not all studies, though, have found a significant



PALMER, HEIBY, FUJII & KAMEOKA

40

association; in a study by Morice and Delahunty (1996),

the correlation between WCST perseverative errors and IQ

was not statistically significant (r = -0.34), and WCST per-

formance impairments appeared to be present independent

of any apparent deterioration in general intelligence from

premorbid levels. However, this study used a small sample

size (n = 17) and may also have been unusual in that while

IQ scores were relatively lower compared to normal con-

trols, the mean IQ for the schizophrenia group was still in

the average range. Furthermore, as schizophrenia is a het-

erogeneous disorder, patterns of cognitive impairment may

differ when looking at different levels of IQ (Weickert et

al., 2000).

Overall, a review of the literature indicates some

equivocal and contradictory findings, and not much is

known about the actual processes that contribute to the

poor WCST performance by persons with schizophrenia.

As current research has yet to fully explain WCST per-

formance impairments, the purpose of this study was to

examine some of the hypothesized underlying cognitive

processes that may contribute to the relatively impaired

executive functioning of individuals with schizophrenia in

a multicultural sample. To this end, measures of attention,

working memory, processing speed, and general intelli-

gence were correlated with executive functioning perform-

ance, as measured by the Wisconsin Card Sorting Test. It

was hypothesized that relatively higher performances on

measures of these cognitive processes would be positively

associated with higher executive functioning performance.

Method

Participants

Participant data was obtained from archived neuropsy-

chological reports from Hawaii State Hospital, a state fo-

rensic and psychiatric hospital serving a multicultural

population.  Subjects had been referred for neuropsy-

chological testing, were found to have adequate vision and

hearing, and completed a neuropsychological battery. A

review of reports from April 1998 to August 2002 yielded

54 subjects. After excluding 9 subjects due to missing data,

a total of 45 subjects remained in the study. At the time of

their evaluation, individuals were either currently in an

inpatient setting at Hawaii State Hospital (n = 43), in an

outpatient setting (n = 1), or in community placement

awaiting trial (n = 1).  There were 37 (82.2%) males and 8

(17.8%) females. The average age was 36.42 (SD = 8.25),

and the average number of years of education was 10.76

(SD  = 2.10). Approximately half of the sample was of

mixed ethnicity (n = 23, 51.1%). Other represented ethnic-

ities included Caucasian (n = 8, 17.8%), Pacific Islander (n

= 7, 15.6%), Asian American (n = 5, 11.1%), and African

American (n = 2, 4.4%). Of those of mixed ethnicity,

common ethnic combinations included individuals classi-

fied as “part Hawaiian” (n = 8, 17.8% of total sample),

Caucasian and Pacific Islander (n = 3, 6.7%), and Asian

American and Caucasian (n = 2, 4.4%).

Within the sample, 33 (73.3%) individuals had a pri-

mary diagnosis of schizophrenia, and 12 (26.7%) had a

diagnosis of schizoaffective disorder. A comorbid sub-

stance abuse or dependence diagnosis was found in a ma-

jority (n = 29, 64.4%) of the participants. Drug use in-

cluded alcohol (n = 18, 40%), marijuana (n = 12, 26.7%),

cocaine (n = 7, 15.6%), methamphetamine (n = 4, 8.9%),

amphetamine (n = 1, 2.2%), inhalants (n = 2, 4.4%), heroin

(n = 1, 2.2%), PCP (n = 1, 2.2%), sedatives (n = 1, 2.2%),

and unspecified polysubstance use (n = 7, 15.6%).

Measures

Indicators of general intelligence, working memory,

and processing speed were derived from Wechsler Adult

Intelligence Scale – Third Edition (WAIS-III; Wechsler,

1997) Full-Scale IQ, Working Memory Index, and Proc-

essing Speed Index scores, respectively. The Working

Memory Index consists of scores on the Arithmetic, Digit

Span, and Letter-Number Sequencing subtests. The Proc-

essing Speed Index consists of the Symbol Search and

Digit Symbol-Coding subtests. The indicator of the cogni-

tive process of attention was derived from the total number

of errors on the Continuous Performance Test of Attention

(CPTA-I), an auditory test of attentional vigilance (Cice-

rone, 1997; Nuechterlein, Buchsbaum, & Dawson, 1994).

The Wisconsin Card Sorting Test (WCST) Categories

Completed score yielded a measure of executive function-

ing.

Procedure

Data collection was based on an archived set of neuro-

psychological reports, which included demographic infor-

mation, psychiatric diagnoses, and cognitive test scores.

Participants were administered standard versions of neuro-

psychological tests by trained hospital staff, from which

scores of cognitive and intellectual functioning were de-

rived. Psychiatric diagnoses were determined from

multidisciplinary group meetings, which routinely included

hospital staff from psychiatry, psychology, nursing, and

additional departments.

Statistical Analyses

Correlational analyses assessed the degree to which

scores of attention, working memory, processing speed,

and general intellectual functioning were associated with

executive functioning. Statistical significance was set at the

p  0.05 level. A data transformation was also conducted

on CPTA-I scores due to non-normal skewness and kurto-

sis; in accordance with Tukey’s ladder of powers (1977), a

square root transformation was able to successfully ap-

proximate normal skewness and kurtosis values for this



EXECUTIVE FUNCTIONING IN SCHIZOPHRENIA

41

distribution. All other variables demonstrated normal dis-

tributions. The contribution of each WAIS-III subtest to the

variance of executive functioning was not computed due to

the sample size.

Results

Individuals with schizophrenia demonstrated impair-

ment on cognitive tests, including the CPTA-I total number

of errors (M  = 33.93, SD = 22.53), WAIS-III Working

Memory Index (M = 78.67, SD = 11.90), WAIS-III Proc-

essing Speed Index (M = 78.36, SD = 9.65), WAIS-III Full-

Scale IQ (M = 78.69, SD = 10.18), and WCST Categories

Completed (M  = 2.91, SD = 1.84). Zero-order correlations

between executive functioning scores and measures of at-

tention (r = -0.23, p = 0.135), working memory (r = 0.18, p

= 0.245), and processing speed (r = 0.21, p  = 0.177)

yielded only non-significant associations, which did not

support the hypothesis that measures of attention, working

memory, and processing speed would help explain or ac-

count for deficits in WCST performance in schizophrenia.

However, executive functioning was significantly corre-

lated with general intellectual functioning (r = 0.39, p  =

0.009). Thus, the hypotheses of this study were partially

supported. A post hoc analysis also found that even after

controlling for attention, working memory, and processing

speed, executive functioning was still significantly corre-

lated with general intellectual functioning (r = 0.36, p  =

0.020).

Discussion

It was hypothesized that relatively higher perform-

ances on measures of attention, working memory, process-

ing speed, and general intellectual functioning would be

positively associated with higher executive functioning

performance, as measured by the Wisconsin Card Sorting

Test (WCST). Contrary to expectations, results indicated

that the specific cognitive processes of attention, working

memory, and processing speed did not significantly corre-

late with executive functioning performance. However,

scores of general intellectual functioning did significantly

correlate with WCST performance, even after controlling

for attention, working memory, and processing speed.

These results suggest that general intellectual deficits may

underlie executive functioning impairments in schizophre-

nia.

The results of this study appear consistent with find-

ings that IQ often correlates with and can often be used to

predict performance on a wide variety of neuropsychologi-

cal tests (Diaz-Asper, Schretlen, & Pearlson, 2004). Even

in healthy, non-clinical samples, IQ scores may be signifi-

cantly associated with WCST performance in adults (Diaz-

Asper et al., 2004; Heaton, 1981) and children (Arffa,

Lovell, Podell, & Goldberg, 1998; Chelune, & Baer, 1986),

although correlations appear more modest than in clinical

samples (Heaton, 1981). However, while general intellec-

tual functioning is often thought to be relatively stable,

remediation studies indicate that the deficits associated

with schizophrenia with respect to WCST performance do

not appear wholly unremediable (Bellack et al., 1990; De-

lahunty et al., 1993; Metz et al., 1994; Perry et al., 2001;

Vollema et al., 1995; Young & Freyslinger, 1995). In addi-

tion, it has been shown that the skills measured on com-

monly used IQ tests are trainable (Staats, 1989; Staats,

1990; Staats & Burns, 1981). Thus, the results of this study

may also suggest the importance of examining cognitive

processes that are associated with each WAIS-III

(Wechsler, 1997) subtest, particularly those not included in

the computation of Working Memory and Processing

Speed Index scores.

Perceptual organization and verbal comprehension, for

example, may contribute to WCST performance. Scores

from individual subtests that compose the WAIS-III Verbal

Comprehension and Perceptual Organization Index scores

were not able to be analyzed in this study due to a small

sample size. However, the skills necessary for each of these

subtests may also be important for WCST performance. For

example, skills measured by WAIS-III verbal subtests not

directly analyzed in this study include distinguishing es-

sential from non-essential detail, using abstract symbols,

and abstract reasoning (Groth-Marnat, 2003). Planning

ability, attention to detail, accurate responding to visual-

spatial material, visual-spatial reasoning, and visual alert-

ness and concentration are other skills measured by WAIS-

III performance subtests (Groth-Marnat, 2003) not directly

analyzed in this study. Furthermore, additional WAIS-III

score configurations, such as Horn’s (1985; Kaufman &

Lichtenberger, 2002) Broad Visualization, as well as Ban-

natyne’s (1974) Spatial Abilities, involve groupings of

subtests not included in the Working Memory and Proc-

essing Speed Index scores. As WCST performance also

involves the use of visual cues, reasoning, and planning,

these skills may prove to be significant contributors to un-

derstanding WCST performance impairment.

It is also possible that cognitive processes not as ex-

plicitly measured by the WAIS-III may be impaired in

schizophrenia and factor into impaired WCST perform-

ance. Cognitive processes, for example, such as concept

formation and attribute identification (Perrine, 1993) or

insight and metacognition (Koren et al., 2004) may better

account for WCST performance impairments in individuals

with schizophrenia. In terms of treatment implications, the

identification of these potentially important cognitive proc-

esses may translate into improved WCST performance and

executive functioning in individuals with schizophrenia.

However, based on the results of this study, it would appear

that a specific focus on improving attention, working mem-

ory, and processing speed may not carry over to improved

WCST performance within this population of individuals

with schizophrenia.

The results of this study may be limited in their gener-

alizability. First, the sample of the present study was drawn

from a relatively understudied multicultural population



PALMER, HEIBY, FUJII & KAMEOKA

42

(Leong, 1989) living in the Hawaiian Islands and thus con-

sisted of a relatively large proportion of individuals of

Asian Pacific Islander descent. As such, related factors that

were not included in the archived data used in this study

(e.g., language proficiency, acculturation, familiarity with

cognitive testing, etc.) may have impacted the statistical

findings of this study. A review of the literature indicates

that few studies have examined WCST performance defi-

cits in ethnic minorities, and, in general, there is a need for

more psychological studies on ethnic minorities (Sue,

1999). This appears particularly relevant as IQ scores vary

across ethnic groups (Lynn, 1996; Suzuki & Valencia,

1997), and ethnic background may predict performance on

neuropsychological tests (Gladsjo et al., 1999). Individuals

from disadvantaged cultural groups may also have higher

rates of schizophrenia (Eaton & Harrison, 2000) and thus

be at more risk for cognitive impairment.

A second characteristic of the sample that may have

implications for generalization is the inclusion of subjects

with dual diagnoses. Individuals with dual diagnoses are

often excluded from neuropsychological studies, which

may not be justified given that significant differences in

WCST performance between non-affective psychotic pa-

tients with and without a dual diagnosis of comorbid sub-

stance use may not exist (Liraud & Verdoux, 2002). In ad-

dition, the high degree of comorbid substance use in indi-

viduals with schizophrenia (Regier et al., 1990) suggests

that many studies to date have looked at only a small subset

of the larger population of individuals with schizophrenia

due to the exclusion of comorbid substance use. Comorbid

substance use in this population may also be of great im-

portance due to its association with poorer functional out-

comes, more frequent hospitalizations, treatment non-

compliance, a more severe course of the disorder, more

severe symptomatology, and increased risk of suicide

(Bartels et al., 1993; Jackson, Fein, Essock, & Mueser,

2001; Mueser, Bellack, & Blanchard, 1992). However, the

research practice of combining data from individuals with

different diagnoses invariably results in an increase in het-

erogeneity and may interfere with targeting what cognitive

processes may be important to consider for executive func-

tioning performance and the impairment that may be asso-

ciated with specific disorders. The interpretation of statisti-

cal findings and the role that various cognitive processes

may play in executive functioning in schizophrenia may

have been clouded by the inclusion of dual diagnosis sub-

jects. Further research examining potential differences be-

tween individuals with schizophrenia with and without

substance abuse problems may help clarify this issue and

whether similar research in the future would benefit from

the inclusion or exclusion of such dual diagnosis subjects.

Several additional limitations of this study may be

noted. Due to the correlational nature of the study, signifi-

cant findings should not be interpreted as evidence of cau-

sation. Also, several potentially relevant factors were not

able to be addressed adequately by the archived data set,

such as diagnostic reliability, medication use, symptom

severity, and the reason for referral for neuropsychological

testing. Executive functioning performance and its relation-

ship to other cognitive processes may differ for individuals

with schizophrenia who are stable and on medications

compared to those with more active and severe symptoms.

Future research may help to address these limitations and

clarify what cognitive processes may help explain WCST

performance in schizophrenia.

Addressing potentially relevant factors such as medi-

cation use and symptom severity, as well as measuring

cognitive processes not addressed in this study, may illus-

trate key aspects to understanding executive functioning

impairment. A comparison of individuals with and without

dual diagnoses may also shed light on the degree to which

executive functioning impairment and its related cognitive

processes may be affected by substance use and have to be

taken into consideration. Furthermore, remediation studies

with individuals with schizophrenia may provide the clear-

est evidence of the best path to cognitive rehabilitation.

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