Table Of ContentC H A P T E R
1
(cid:1)
Overview of the WAIS IV/
(cid:1)
WMS IV/ACS
Lisa Whipple Drozdick, James A. Holdnack,
Lawrence G. Weiss and Xiaobin Zhou
Pearson Assessment, San Antonio, Texas, USA
INTRODUCTION
The Wechsler Adult Intelligence Scale(cid:1)Fourth Edition (WAIS(cid:1)IV:
Wechsler, 2008) and the Wechsler Memory Scale(cid:1)Fourth Edition
(WMS(cid:1)IV: Wechsler, 2009), combined with other measures, are fre-
quently used in comprehensive evaluations. This book is about best
practices in using these instruments together, and introduces advanced
clinical solutions specific to neuropsychological evaluations. The
Advanced Clinical Solutions for WAIS(cid:1)IV and WMS(cid:1)IV (ACS:
Pearson, 2009) and the WMS(cid:1)IV Flexible Approach (WMS(cid:1)IV Flex:
Pearson, 2010) expand the constructs assessed across the two instru-
ments for use with specific neurodiagnosticquestions.
This chapter assumes the reader has basic knowledge of WAIS(cid:1)IV
and WMS(cid:1)IV subtests, administration, and general interpretative
strategies. Detailed descriptions of the subtests and composites are
available elsewhere (see Coalson, Raiford, Saklofske, & Weiss, 2010;
Drozdick, Wahlstrom, Zhu, & Weiss, 2011; Wechsler, 2008, 2009). This
chapter presents a more in-depth overview of the constructs measured
by the WAIS(cid:1)IV and WMS(cid:1)IV, goes beyond the numbers to explore
cognitive factors that influence performance on each of the major clini-
cal domains assessed, and introduces more advanced procedures not
found in the WAIS(cid:1)IV and WMS(cid:1)IV administration and technical
manuals. Following this high level presentation of the instruments,
WAIS-IV,WMS-IV,andACS.
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DOI:http://dx.doi.org/10.1016/B978-0-12-386934-0.00001-8 ©2013ElsevierInc.Allrightsreserved.
2 1. OVERVIEWOFTHEWAIS(cid:1)IV/WMS(cid:1)IV/ACS
information on the joint factor structure of the combined instruments
is described. The chapter concludes with descriptions of ACS and
WMS(cid:1)IV Flex.
WAIS(cid:1)IV CONTENTAND APPROACH TO
DEVELOPMENT
In a continuation of the evolution of the Wechsler model, the
WAIS(cid:1)IV index scores are the primary focus of clinical
interpretation. ThisisashiftfromtheoriginalWechslermodelofintelli-
gence, which was based on a two-part structure comprised of the
Verbal Intelligence Quotient (VIQ) and Performance Intelligence
Quotient (PIQ). The current Wechsler factor model includes four fac-
tors: Verbal Comprehension, Perceptual Reasoning, Working Memory,
and Processing Speed. The shift in focus to more specific factor-based
indexes began in 1991 when the WISC(cid:1)III introduced four factor-based
index scores as an optional alternative to the traditional VIQ/PIQ
structure; the WAIS(cid:1)III followed suit in 1997. In 2003, the WISC(cid:1)
IV dropped VIQ and PIQ, eliminating them from the test in favor
of the four factor-based structures presented in WISC(cid:1)III. In addition,
the name of the Freedom from Distractibility Index was changed to
the Working Memory Index to reflect the increasing understanding
of the construct. The name of the Perceptual Organization Index was
changed to the Perceptual Reasoning Index to accurately describe the
increased focus on perceptual reasoning among the newly created
perceptual subtests, and clinical interpretation was focused on the four
index scores. The WAIS(cid:1)IV adopted the four-factor model in 2008,
completing thetransformationof the Wechslerseries of tests.
To be fair to Dr. Wechsler’s legacy, his model has always included
subtests which measure working memory and processing speed,
just not in the current index structure reflected in WAIS(cid:1)IV. These
measures were included in the VIQ and PIQ structures depending
on whether the stimuli and response processes were verbal or
visual(cid:1)perceptual, respectively. Contemporary researchers have devel-
oped well-articulated theories about the underlying neurocognitive pro-
cesses tapped by these tasks and their relation to intelligence. Original
Wechsler subtests such as Arithmetic and Digit Span are now under-
stood as measures of working memory; and Coding, or Digit Symbol as
it was originally named, is now understood as a measure of cognitive
processing speed. As more was learned about the importance of these
constructs in the expression of intelligent behavior, the Wechsler tests
adapted by disentangling these constructs from other skills included in
the VIQ and PIQ. New tasks such as Letter Number Sequencing and
WAIS-IV,WMS-IV,ANDACS
WAIS(cid:1)IVINDEXSCORESANDSTRUCTURE 3
Cancellation were added to expand the assessment of working memory
and processing speed, respectively. Also, Digit Span was significantly
revised in WAIS(cid:1)IV to include digit sequencing items to improve the
assessment of working memory based on our current understanding of
that construct.
Similarly, several long-standing Wechsler subtests are believed to be
related to fluid reasoning (i.e., Similarities, Block Design). Subsequently,
new subtests have been developed to measure this construct more
directly such as Matrix Reasoning (which first appeared in WISC(cid:1)III
and was subsequently included in WISC(cid:1)IV, WAIS(cid:1)III, and
WAIS(cid:1)IV), Picture Concepts (which first appeared in WISC(cid:1)IV and
then was added to WPPSI(cid:1)III), and Figure Weights and Visual Puzzles
which debuted in the WAIS(cid:1)IV.
Without Dr. Wechsler’s far-reaching clinical insights, the field of
intellectual assessment would not be where it is today. However, the
WAIS(cid:1)IV is a different test then the one that Dr. Wechsler introduced,
one that builds upon multiple modern theories of cognitive neurosci-
ence and is informed by ongoing clinical and neuropsychological
research.
WAIS(cid:1)IV INDEX SCORES AND STRUCTURE
Figure 1.1 presents a visual model of the WAIS(cid:1)IV. The composite
scores, comprised of the four index scores and Full Scale Intelligence
Quotient (FSIQ), are presented in ovals and are the primary focus of
interpretation. The subtests are listed below the index in which they are
Full Scale
Verbal Perceptual Working Processing
Comprehension Reasoning Memory Speed
Index Index Index Index
Similarities Block Design Digit Span Symbol Search
Vocabulary Matrix Reasoning Arithmetic Coding
Information Visual Puzzles (Letter-Number (Cancellation)
(Comprehension) (Figure Weights) Sequencing)
(Picture Completion)
FIGURE1.1 WAIS(cid:1)IVFactorModel.
WAIS-IV,WMS-IV,ANDACS
4 1. OVERVIEWOFTHEWAIS(cid:1)IV/WMS(cid:1)IV/ACS
included. Parentheses are used to differentiate supplemental subtests
from the core subtests usedto derive indexscores.
Verbal Comprehension Index
The Verbal Comprehension Index (VCI) reflects an individual’s abil-
ity to comprehend verbal stimuli, reason with semantic material, and
communicate thoughts and ideas with words. Such abilities are impera-
tive for intelligent functioning in modern society. As shown in
Figure 1.1, the VCI consists of the Similarities (SI), Vocabulary (VC),
and Information (IN) subtests. The Comprehension (CO) subtest is sup-
plemental. All VCI subtests are well-known and researched measures
ofverbal comprehension.
Perceptual Reasoning Index
The Perceptual Reasoning Index (PRI) measures fluid reasoning
along with some perceptual organization. Required WAIS(cid:1)IV subtests
are Block Design (BD), Matrix Reasoning (MR), and Visual Puzzles
(VP). The Figure Weights (FW) subtest is supplemental. Block Design
and MR are well-known measures of visual(cid:1)spatial organization and
fluid reasoning, respectively.
Two subtests are new to WAIS(cid:1)IV: Visual Puzzles and
Figure Weights. Visual Puzzles measures the ability to analyze and syn-
thesize abstract, nonverbal, visual material. Successful performance
requires the ability to maintain a visual image in mind temporarily
while mentally rotating, inverting, and otherwise manipulating that
image and matching the resulting percept to a visual target. It also
requires the integration of multiple related cognitive processes includ-
ing visual perception, simultaneous processing, working memory, spa-
tial visualization, spatial manipulation, and visuoconstruction abilities.
Figure Weights measures quantitative and analogical reasoning.
Quantitative reasoning tasks can involve fluid reasoning processes
expressed as mathematical processes, emphasizing either inductive or
deductive logic. Although the solution to each FW item can be
expressed with algebraic equations, there is no task requirement to do
so,eliminatingthedemandforacquired knowledgeofadvancedmathe-
matical equations. Figure Weights involve working memory, but it is
reduced relative to typical quantitative tasks (e.g., mental arithmetic)
through the continual visual presentation of items in a stimulus book
that allows the patient to refresh stimuli held in working memory while
solving theproblem.
WAIS-IV,WMS-IV,ANDACS
WAIS(cid:1)IVINDEXSCORESANDSTRUCTURE 5
Working Memory Index
The Working Memory Index (WMI) measures attention, concentra-
tion, and working memory. The WMI consists of two primary subtests,
Digit Span (DS) and Arithmetic (AR), and the supplemental Letter-
Number Sequencing (LN). The DS subtest includes three tasks: Digit
Span Forward (DSF), Digit Span Backward (DSB), and the new Digit
Span Sequencing(DSS).DSF measures short-term memory, notworking
memory. DSB and DSS measureauditory working memory.The current
reformulation of the AR subtest represents a substantial transformation
from previous editions and is a much improved measure of working
memory. Compared to its predecessors, the WAIS(cid:1)IV AR subtest con-
tains reduced verbiage in the word problems, fewer items with time
bonuses, and simpler numerical calculations with more steps, reducing
the pull of mathematical skill and increasing the activation of working
memory.
Processing Speed Index
The Processing Speed Index (PSI) measures the speed of mental pro-
cessing, using visual stimuli and graphomotor skills, and is related to
the efficient use of other cognitive abilities. Aweakness in simple visual
scanning and tracking may leave a patient less time and mental energy
for the complex task of understanding new material. The PSI includes
the core Coding (CD) and Symbol Search (SS) subtests and the
supplemental Cancellation (CA) subtest. Cancellation is similar to pre-
viously developed cancellation tasks designed to measure processing
speed, visual selective attention, vigilance, perceptual speed, and
visual(cid:1)motor ability (Bate, Mathias, & Crawford, 2001; Geldmacher,
Fritsch, & Riedel, 2000; Sattler, 2008; Wojciulik, Husain, Clarke, &
Driver, 2001). Cancellation tasks have been used extensively in neuro-
psychological settings as measures of visual neglect, response inhibi-
tion, and motor perseveration (Adair, Na, Schwartz, & Heilman, 1998;
Geldmacher et al., 2000; Lezak, Howieson, & Loring, 2004; Na, Adair,
Kang, Chung, Lee, & Heilman, 1999). Relative to the WISC(cid:1)IV version
of CA, a decision-making component was added in the WAIS(cid:1)IV to
place more complex cognitive demands on examinees. The patient must
simultaneously discriminate both the color and the shape of the stimuli
andinhibit responding when only one of the two features ispresent.
General Ability Index
The General Ability Index (GAI) summarizes performance on the
VCI and PRI in a single number. These two indexes are traditionally
WAIS-IV,WMS-IV,ANDACS
6 1. OVERVIEWOFTHEWAIS(cid:1)IV/WMS(cid:1)IV/ACS
thought to contain the most highly ‘g’-loaded subtests within
WAIS(cid:1)IV. As discussed later however, AR has moved up considerably
in the ranking of g-loadings, but is not included in GAI. The WAIS(cid:1)IV
GAI excludes the contributions of the WMI and PSI to intelligence.
Clearly, GAI and FSIQ can lead to different impressions of a patient’s
overall ability when there is variability across the four indexes.
The GAI was first developed for use with WISC(cid:1)III in ability-
achievement discrepancy analyses (Prifitera, Weiss, & Saklofske, 1998)
because many students with learning disability (LD) exhibit cognitive
processing deficits in working memory and processing speed concomi-
tant with their learning disabilities. This pattern can result in lower
FSIQ scores for individuals with LD, and consequently smaller discre-
pancies with achievement, thus making it less likely that he or she will
be identified as underachieving and in need of services. Thus, use of
GAI as a measure of global intelligence for comparisons with other abil-
ities impacted by lower performance on working memory and proces-
sing speed, such as achievement, is often a more appropriate
comparisonwith thoseconstructsthan FSIQ.
Other uses for the GAI have since been identified. For example, GAI
may be an appropriate estimate of overall ability when physical or sen-
sory disorders invalidate performance on the working memory or pro-
cessing speed tasks, or both. Another possible use is in approximating
the pre-injury cognitive status and memory abilities of patients with
traumatic brain injury. All discrepancies between the WAIS(cid:1)IV and
WMS(cid:1)IV utilize the GAI in place of the FSIQ. Memory impairment is
often compromised in the same clinical conditions where low WMI and
PSI scores are observed (e.g., moderate-to-severe traumatic brain injury:
TBI). Similar to the differences observed in LD evaluations, when FSIQ
is lower due to comparatively low WMI and PSI scores, it is more diffi-
cult to find differences between intellectual functioning and memory
functioning. The VCI and PRI tend to be less affected in clinical disor-
ders in which memory functioning is also impacted. The use of GAI
allows the practitioner to better identify memory deficits in patients
with concomitant PSI and/orWMI deficits.
Prifitera, Saklofske and Weiss (2005) suggest that some practitioners
may prefer the GAI as an alternative way of summarizing overall abil-
ity. This suggestion has led to an increasing number of psychological
evaluations in which the GAI is described as a better estimate of overall
ability than FSIQ whenever the WMI or PSI scores are significantly
lower than the VCI or PRI scores. As subsequently clarified, this is not
what the authors intended (Prifitera, Saklofske, & Weiss, 2008). The
GAI should be considered a better estimate of intelligence than FSIQ
only when there are sound clinical reasons to exclude WMI and PSI,
such as invalid administration due to lack of effort, sensory or physical
WAIS-IV,WMS-IV,ANDACS
7
ISSUESINSUMMARIZINGOVERALLABILITY
impairments, or disturbance of the testing session. Working memory
and processing speed are essential components of a comprehensive
assessment of intelligence, and excluding them from the estimate of
overall intelligence simply because the patient’s abilities in those areas
are relative weaknesses is poor practice. Such practice will result in
unrealistically high estimates of intelligence for these patients, possibly
excluding them from needed services and creating unrealistic employ-
ment expectations. The GAI can be a vital comparison measure in
an evaluation when described correctly; however, it is not the best esti-
mate of overall intelligence because it suffers from construct
underrepresentation.
Cognitive Proficiency Index
The Cognitive Proficiency Index (CPI) summarizes performance on
the working memory and processing speed indices of the WAIS(cid:1)IV in
a single score. The CPI represents a set of functions whose common ele-
ment is the proficiency with which one processes certain types of cogni-
tive information. Proficient processing, through quick visual speed and
good mental control, facilitates fluid reasoning and the acquisition of
new material by reducing the cognitive demands of novel or higher
order tasks (Weiss, Saklofske, Prifitera, & Holdnack, 2006). In other
words, efficient cognitive processing facilitates learning and problem-
solving by “freeing up” cognitive resources for more advanced, higher
level skills.
The WAIS(cid:1)IV CPI excludes the contributions of verbal comprehen-
sion and perceptual reasoning to intelligence. Thus, CPI and GAI can
provide different views into a patient’s cognitive abilities when there is
significant variability across the relevant index scores. Both views are
sometimes necessary to form a complete picture of an individual’s
strengths and weaknesses that is not distorted by combining a set of
diverse abilities into a single overall score. Rather than reporting GAI
as the best estimate of overall ability when the profile of abilities is
diverse, it is sometimes better practice to describe both the GAI and
CPI in the psychologicalevaluation. Norms tables for the WAIS(cid:1)IV CPI
are provided in Weiss, Saklofske,Coalson and Raiford (2010).
ISSUES IN SUMMARIZING OVERALL ABILITY
The FSIQ has strong explanatory and predictive power at the group
and individual level. Still, the use of an overall summary score may
mask individual differences among the broad domains of general
WAIS-IV,WMS-IV,ANDACS
8 1. OVERVIEWOFTHEWAIS(cid:1)IV/WMS(cid:1)IV/ACS
ability, especially in patients with neuropsychological deficits where the
focus of clinical attention is not prediction but diagnosis of underlying
cognitive deficits. For this reason, the relevance of reporting IQ scores
has been questioned (Fiorello et al., 2007). Yet, otherresearchers suggest
that FSIQ may be an equally valid measure of general ability for indivi-
duals or groups having highly variable index scores as for those having
consistent index scores (Daniel, 2007) and that there may be no differ-
ence in the predictive validity of FSIQ for low-scatter and high-scatter
groups (Watkins,Glutting, &Lei, 2007).
FSIQ is an especially strong predictor of educational attainment,
occupational level, memory functioning, and school achievement
(Wechsler, 2008, 2009). FSIQ and achievement, for example, correlate
strongly, typically around 0.70. This means that FSIQ explains about
half the variance in achievement. There is no known variable or collec-
tion of variables that comes close to fully accounting for the other half.
Beyond the relationship with achievement, there is considerable eco-
logicalandcriterion validityfortheuseofanoverallestimateofgeneral
intelligence in a variety of areas related to success in life including pre-
employment testing and predicting job performance (Gottfredson, 1997,
1998; Kuncel, Hezlett, & Ones, 2004). Thus, when the focus of clinical
attention is prediction then FSIQ is often the most potent predictor.
When the focus is clinical diagnosis of pathology then the index scores
areoftenmore informative.
UnlikeeveryotherWechslerinterpretativesystemthathasbeenwrit-
ten, we discuss FSIQ last, rather than first. This is not to devalue the
explanatory and predictive power of the FSIQ, but to emphasize the
descriptive clinical power of the WAIS(cid:1)IV Indexesand to place FSIQ in
its proper role of providing a relevant backdrop against which the
index scores are evaluated. This is consistent with our position that the
first line ofclinical interpretation restswith theindexscores.
A POSSIBLE FIFTH FACTOR
Several studies have explored the WAIS(cid:1)IV factor model. Benson,
Hulac and Kranzler (2010) argued for the superiority of a five-factor
model in which Matrix Reasoning, Figure Weights, and Arithmetic
loaded on a fifth factor termed Fluid Reasoning. Ward, Bergman and
Herbert (2011) proposed a modification of the WAIS(cid:1)IV four factor
model in which residual factors were formed for visual(cid:1)spatial reason-
ing (BD, VP, and PC) and quantitative reasoning (FW and AR). Ward
and colleagues argued that this modified model was theoretically con-
sistent yet superior to the original WAIS(cid:1)IV model, but that there
was no compelling statistical reason to prefer the Benson et al. (2010)
WAIS-IV,WMS-IV,ANDACS
9
APOSSIBLEFIFTHFACTOR
five-factor model over the modified four-factor model. Weiss, Keith,
Chen, and Zhu (2013a) tested a five-factor model in which quantitative
reasoning (AR and FW) was defined as a narrow ability subsumed
under the fluid reasoning factor (MR, FW, and AR). Weiss et al. found
that although the fit was slightly better for this model, it was excellent
for both the four and five factor models. They extended previous find-
ings by demonstrating full measurement invariance between normal
and clinical samples for both models. The above studies included the
supplemental subtests, which is clearly best practice for model defini-
tion but often of limited utility to practitioners who have administered
only the core subtests. Using only core WAIS(cid:1)IV subtests,
Lichtenberger and Kaufman (2009) proposed a five-factor model in
which the fluid factor consists of MR and AR (without FW that is
supplemental).
These WAIS(cid:1)IV studies should be interpreted in light of the literature
on the WISC(cid:1)IV factor structure because the two tests have the same
conceptual model, albeit with a couple of different subtests. Extant
research on WISC(cid:1)IV factor structure contains a similar set of findings
as WAIS(cid:1)IV: both four- and five-factor models emerge as good fits to
the data, and the fifth factor is often characterized as fluid reasoning;
although complicated by the interpretation of Arithmetic as fluid or
quantitative reasoning (Bodin, Pardini, Burns, & Stevens, 2009; Chen,
Keith, Chen, & Chang, 2009; Chen, Keith, Weiss, Zhu, & Li, 2010; Chen,
& Zhu, 2012; Keith, Fine, Taub, Reynolds, Kranzler, 2006; Lecerf, Rossier,
Favez,Reverte,&Coleaux,2010;Weiss,Keith,Chen,&Zhu,2013b).
It is interesting to observe how the g-loadings of Wechsler subtests
shift as the composition of subtests shifts with each new edition of the
test. While it has been axiomatic for decades that VC and BD are the
most highly g-loaded subtests on the Wechsler scales, AR now emerges
as one of the three highest g-loading subtests in WAIS(cid:1)IV studies, even
ranking first in some studies. Arithmetic isclearly a factorially complex,
multiply determined task that requires the integration of several cogni-
tive abilities including verbal conceptualization, working memory, and
numerical reasoning; and perhaps the integrative task demands are
what make the AR subtest partly fluid in nature. At the same time, the
numerical stimuli of the AR task logically invokes interpretations based
partly on quantitative reasoning, considered as a subtype of fluid rea-
soning in the Cattell, Horn, Carroll (CHC) model of intelligence
(Carroll, 1993).
While the clinical interpretation of a possible fifth factor requires fur-
ther research, the main point for clinicians to keep in mind is that when
patients present large discrepancies between the subtests that compose
the PR or WM indexes, there is some empirical support for interpreting
these patterns. When the BD and VP scores hang together separately
WAIS-IV,WMS-IV,ANDACS
10 1. OVERVIEWOFTHEWAIS(cid:1)IV/WMS(cid:1)IV/ACS
from MR and FW, consider interpretations based on visual(cid:1)spatial
organization versus fluid reasoning. When AR is aberrant within the
WMI but hangs together with FW, consider interpretations based on
quantitative reasoning versus working memory.
WAIS(cid:1)IV: GOING BEYOND THE NUMBERS
Cognitive Influences on VCI
Although the VCI includes tasks that require prior knowledge of cer-
tain words and information, it would be a mistake to interpret this
index only as a measure of words and facts taught in school. Clearly,
some base knowledge of words must be assumed in order to measure
verbal reasoning; after all, one could not measure verbal reasoning
without using words. Barring an unusually limiting environment, per-
formance on these tasks reflects a person’s ability to grasp verbally pre-
sented facts typically available in the world around them, to reason
with semantic constructs, and to express their reasoning with words.
VCI measures crystallized knowledge, the breadth and depth of a per-
son’s acquired knowledge of a culture, and the effective application of
this knowledge. This store of primarily verbal or language-based
knowledge may represent abilities developed largely through the
investment of other abilities during educational and general life experi-
ence (McGrew & Flanagan, 1998, p. 20).
A low score on VCI may reflect low verbal comprehension or expres-
sion ability, a lack of opportunity to develop particular verbal abilities,
or some kind of “interference” that compromises the acquisition or
expression of abilities (e.g., traumatic brain injury, mild cognitive
impairment, aphasia, epilepsy). Prior to making an interpretation of
lowverbalability, thepsychologist shouldask:was therequiredknowl-
edge acquired but cannot be recalled (for several possible reasons) or
was it never acquired in the first place? One useful methodology for
addressing this issue is the “recognition paradigm.” All of the
WAIS(cid:1)IV verbal comprehension subtests require free recall of verbal
information, which is a much more difficult cognitive task than cued
recall or recognition. Some individuals may answer incorrectly because
they could not retrieve information from long-term storage even though
they know the information. In thesecases, the information may be more
readily recalled if a clue is given or the correct information can be
selected from a set of possible answers. This can be observed in every-
day situations when someone struggles to recall the name of a col-
league. However, recall improves when additional clues are provided,
such as the university he or she is from or the initial letter-sound of his
WAIS-IV,WMS-IV,ANDACS
