About the WISC IV: Who Are the Gifted
Using the New WISC-IV?
Linda Kreger Silverman, Ph.D.
Barbara (“Bobbie”) Gilman. M.S.
R. Frank Falk, Ph.D.
Gifted Development Center
Each generation of IQ tests by the various test publishers is eventually revised
and renormed, with a test possibly being completely reformulated. We are in the
transition phase now, using a whole new series of tests and finding what works
and doesn’t work, or which portions to utilize to satisfy various needs. As
always, the tests represent both improvements and losses for the gifted. We have
seen some extension of test ceilings, which benefits the gifted, and increased
emphasis on processing skills, which does not.
Wechsler tests continue to be good initial IQ tests for the gifted. Although
they rarely yield scores above the 140s, they offer good diagnostic information,
and indications of ability beyond their limits. The Wechsler Intelligence Scale
for Children-Fourth Edition (WISC-IV), released in August of 2003, replaces the
WISC-III. School districts usually have one year, according to American
Psychological Association (APA) standards, to begin using a newer version of an
IQ test. Therefore, most school districts that employ Wechsler tests should have
begun using the new edition this fall.
Compared to the WISC-III, the WISC-IV is a
substantial reformulation. While the highest IQ score possible is still 160, the
WISC-IV does offer additional harder questions at the upper ends of a number of
subtests. The Verbal IQ and Performance IQ scores of its predecessors have been
eliminated. The 10 required subtests yield a Full Scale IQ score and four
Composite scores: Verbal Comprehension, Perceptual Reasoning, Working Memory and
Processing Speed. The Verbal Comprehension and Perceptual Reasoning Composites
are very good indicators of giftedness. They do an admirable job of assessing
verbal abstract reasoning and provide very useful tests of visual reasoning with
less timing emphasis. Working Memory and Processing Speed are less correlated
with giftedness. The five supplementary tests add flexibility; two substitutions
are allowed in different composite areas in deriving Full Scale IQ scores. The
Dumont-Willis Indices (http://alpha.fdu.edu/psychology/) offer another approach
to evaluating WISC-IV scores besides the Full Scale IQ when Verbal Comprehension
and Perceptual Reasoning Composite scores are higher than Working Memory and
Processing Speed (the WISC-IV Technical Manual suggests this will usually be the
case). The Dumont-Willis Index-1 (DWI-1) score can be computed for the
combination of Verbal Comprehension and Perceptual Reasoning, while a DWI-2
score can be computed for the combination of Working Memory and Processing
Speed. These computations, based on the Tellegen and Briggs formula, could be
helpful to schools. The DWI-1 score would be an excellent identifier of gifted
children for school programs, and only six subtests of the WISC-IV are needed to
The WISC-IV is yielding many gifted-level
scores at the Gifted Development Center. However, some of the Full Scale IQ
scores are excessively lowered by Working Memory and Processing Speed scores. As
intelligence is primarily abstract reasoning ability, emphasizing short-term
auditory memory and processing speed on paper-and-pencil tests is less helpful.
Two Working Memory subtests (only one was required on the WISC-III) and two
Processing Speed subtests (only one was required on the WISC-III) place more
weight on these processing skills in the Full Scale IQ score. This is
unfortunate for gifted children and confounds the Full Scale IQ Score (FSIQ) as
a gifted identifier.
In the normative sample for the WISC-IV, the gifted group (which had scored at
least 130 previously) earned a Full Scale IQ score of 123.5 on the WISC-IV.
Comprehension score was 124.7 and Perceptual Reasoning score was 120.4. However,
in line with our experience, their Working Memory averaged only 112.5 and their
Processing Speed was 110.6 (WISC-IV Technical Manual, p. 77).
The Increased Emphasis on Processing Skills
Perhaps the inclusion of more processing
skills measures is appropriate for lower functioning children. If the child's
processing speed on paper-and-pencil tasks is so slow that he or she cannot
complete work in a reasonable amount of time in the classroom, processing speed
may be such a limiting factor that it should be included in IQ scores.
Likewise, if short-term auditory memory is so poor that the teacher's
instructions can't be retained at all, this is a significant problem. However,
gifted children rarely perform extremely poorly in these areas on an absolute
scale. It makes much more sense to identify them as gifted based on assessments
emphasizing reasoning, provide them gifted learning experiences, and then add
any accommodations based on relative weaknesses to the gifted accommodations.
A Full Scale IQ score that averages gifted
reasoning and average processing skills fails to identify either the giftedness
or the relative weaknesses. Test authors have
wrongly assumed that gifted children are fast processors. Some are very quick;
others are reflective or perfectionistic, slowing their speed. Gifted children
also show a preference for meaningful test materials, and may not perform well
on short-term memory tests or other tasks that utilize non-meaningful material.
They usually perform so much better with meaningful material that their scores
with non-meaningful material are difficult to interpret.
The higher a child’s intelligence, the more
reasonable it would be to assume that the child would score well in all four of
the indices. However, as noted above, the gifted group in the normative sample
scored in the superior ranges on Verbal Comprehension and Perceptual Reasoning,
but considerably lower in Working Memory and Processing Speed. Presumably some
group other than the gifted scored in the superior ranges in these two strands,
but this introduces a confounding variable into the Full Scale IQ score.
The two lower indices do not reflect the abilities of the gifted and tend to
lower their Full Scale scores. Given these issues, it will be a challenge for
testers of the gifted to choose 2tests appropriate to document gifted strengths
and diagnose weaknesses, without eliminating children from gifted program
Dawn Flanagan and Alan Kaufman (2004), in Essentials of WISC-IV Assessment,
argue that the Full Scale IQ (FSIQ) should not be reported if the variance from
the highest to lowest composite score is 23 points or greater. The gifted group
in the WISC-IV normative sample showed a 13-point discrepancy, suggesting the
likelihood of many gifted children whose FSIQs should not be used.
The Gifted Development Center’s (GDC)
research with 103 children (Falk, Silverman & Moran, 2004) yielded even larger
discrepancies. Their significance is evident when the
results are compared with those of a control group in the normative sample:
GDC Control Group in Norm Sample
Verbal Comprehension Index 131.7 106.6
Perceptual Reasoning Index 126.4 105.6
Working Memory Index 117.7 103.0
Processing Speed Index 104.3 102.8
Full Scale 127.2 106.7
(WISC-IV Technical Manual, p. 77)
There is little variation in the indices of the control group: less than 4 IQ
points between highest and lowest subtest scores. Note that the Working Memory
and Processing Speed Indices do not deflate the Full Scale IQ scores. On the
contrary, the Full Scale mean is actually higher than the highest index. By
comparison, the mean discrepancy between highest and lowest subtest scores in
the gifted sample was 27.4 points. Nearly 60% of the sample had discrepancies
between the Verbal Comprehension Index and the Processing Speed Index of 23
points. Discrepancies ranged as high as 69 points—over 4 standard deviations. It
is also revealing that while the gifted group demonstrated a 25-point advantage
over the control group in verbal abstract reasoning, their differences in
Processing Speed were negligible: less than 2 points. It is obvious that gifted
students do not perform faster on these processing speed tasks than average
students. Of the four indices, the Verbal Comprehension Index is clearly the
best indicator of giftedness and the Perceptual Reasoning Index is the second
best indicator. The mean Full Scale IQ score of the gifted sample was definitely
depressed below the gifted range, even though the mean Verbal Comprehension
Index was high enough to qualify these students for gifted services. By these
scores, a general rule might be to eliminate consideration of the Full Scale IQ
for gifted identification.
Flanagan and Kaufman (2004) suggest using
the General Ability Index (GAI) instead, which, like the DWI-1 of Dumont and
Willis, utilizes only the Verbal Comprehension and Perceptual Reasoning scores.
This is now being supported by trainers for Harcourt 3Assessments (PsychCorp).
If the GAI table from Flanagan and Kaufman’s book were used to combine the mean
Verbal Comprehension and Perceptual Reasoning Indices from the Gifted
Development Center study (131.7 + 126.4), the resulting mean GAI of the gifted
group would be 132, which qualifies for gifted services.
Subtests Most Appropriate for Gifted Assessment The following chart indicates
the strongest subtests for the gifted population in two different studies.
(Subtests in parentheses are optional.)
WISC-IV Subtest Means of 63 Gifted Children in the Norm Sample compared with 103
Gifted Children from GDC Gifted Norm Group GDC
Similarities 14.1 15.8
Vocabulary 14.6 15.4
Comprehension 14.1 14.8
Matrix Reasoning 13.4 14.7
Picture Concepts 12.7 14.6
(Arithmetic) 14.2 14.1
(Information) 13.9 14.1
Block Design 13.8 13.2
(Word Reasoning) 13.2 12.9
Letter-Numb. Sequencing 12.6 12.9
(Picture Completion) 13.0 12.5
Symbol Search 12.1 11.5
Digit Span 12.0 12.3
(Cancellation) 11.0 10.3
Coding 11.5 9.9
(WISC-IV Technical Manual, p. 77)
Similarities, Vocabulary and Comprehension make up the three required subtests
to derive the Verbal Comprehension Index. Please note that, in both studies,
these three subtests emerged among the highest scores for the gifted groups.
Matrix Reasoning, Picture Concepts and Block Design, which make up the three
required subtests to derive the Perceptual Reasoning Index, appear to be among
the next strongest set of required (not optional) subtests. Picture Concepts
fared considerably better with the Gifted Development Center sample than with
the gifted group in the norm sample. In the norm sample, Arithmetic surpassed
all but Vocabulary, and in the Gifted Development Center sample, it ranked in
sixth place. Additional information about Arithmetic can be found in the factor
loadings on general intelligence. Note that it holds the highest rank as a
measure of general intelligence.
4Good Measures of g
Fair Measures of g
Matrix Reasoning .687
Block Design .672
Word Reasoning .648
Letter-Number Seq. .621
Picture Completion .616
Picture Concepts .582
Symbol Search .568
Digit Span .525
Poor Measure of g
Poorest Measure of g
(Keith, Fine, Taub, Reynolds, & Kranzler, 2004)
Combining information from the performance
of two sets of gifted students with the factor loadings on general intelligence,
it becomes clear that Arithmetic is a much
stronger measure of giftedness than Letter-Number Sequencing or Digit Span, the
two required subtests for deriving the Working Memory Index. While Letter-Number
Sequencing has a higher rank than Digit Span in loading on general intelligence,
Digit Span produces more predictable and interpretable responses from students.
LetterNumber Sequencing involves listening to a random list of letters and
numbers, separating them and manipulating them in a prescribed way. An
occasional response to the task is, “You want me to do what?” One boy took over
3 minutes each for the last few items and stated that he felt nauseated
Therefore, at the Gifted Development Center, we substitute Arithmetic for
Letter-Number Sequencing in most assessments. If a child appears to be
mathephobic, we do not do the substitution. Two substitutions are allowable to
derive a Full Scale IQ score, as long as they reflect an a priori judgment
before the test is administered (or unless a subtest becomes spoiled in
The new Cancellation item is not particularly useful in assessing giftedness, as
can be seen from both the performance of the two gifted groups and its extremely
low standing as a measure of general intelligence. It is even less correlated
with general intelligence than the Mazes subtest, which was removed from the
WISC-IV. The Gifted Development Center uses this optional subtest only on rare
occasions for diagnostic purposes. Unfortunately, the Coding subtest, which has
never been a good predictor of giftedness in previous versions of the WISC (Kaufman,
1992), continues to be a required subtest on the WISC-IV. As can be seen from
both studies and the factor loadings, Coding is a poor measure of general
intelligence and serves to diminish scores of gifted students, whose speed of
performance on clerical paper and pencil tasks is rarely as well developed as
their conceptual abilities. This asynchrony in development is typical of the
gifted population (Silverman, 1993), and another reason why processing speed
should not play a role in the assessment of giftedness.
The studies conducted to date on the WISC-IV suggest that two of the four
indices, the Verbal Comprehension Index and the Perceptual Reasoning Index,
provide the best measures of giftedness. Therefore, it seems prudent to
administer only 6 subtests of the WISC-IV for selection to gifted programs:
Vocabulary, Similarities, Comprehension, Matrix Reasoning, Picture Concepts and
Block Design. The General Ability Index (GAI) can be derived from these six
subtests, and is recommended by both the test publisher and the new Essentials
of WISC-IV Assessment by Flanagan and Kaufman (2004). They advise using the GAI,
instead of the Full Scale IQ, if the 4 composite scores vary by 23 or more
points, and if the Verbal Comprehension Index and the Perceptual Reasoning Index
vary by less than 23 points. Dumont and Willis also advise that their DWI-1 and
should only be calculated if the scores that go into them are relatively close.
This short form of the WISC-IV will be less expensive to administer, less time
consuming, more efficient and will yield more accurate estimates of the
abilities of gifted students, without the confounding variables of Working
Memory and Processing Speed.
Falk, R. F., Silverman, L K., & Moran, D. (2004, November). Using two WISC-IV
indices to identify the gifted. Paper presented at the 51st
Annual Convention of the National Association for Gifted Children, Salt Lake
Flanagan, D. P., & Kaufman, A. S. (2004). Essentials of WISC-IV assessment.
Hoboken, NJ: John Wiley & Sons.
Kaufman, A. S. (1992). Evaluation of the WISC-III and WPPSI-R for gifted
Roeper Review, 14, 154-158.
Keith, T. Z., Fine, J. G., Taub, G. E., Reynolds, M. R., & Kranzler, J. H.
(2004). Hierarchical multi-sample, confirmatory factor analysis of the Wechsler
Intelligence Scale for
Children-Fourth Edition: What does it measure? (Manuscript submitted for
Silverman, L. K. (1993). The gifted individual. In L. K. Silverman (Ed.),
Counseling the gifted & talented (pp. 3-28). Denver: Love.
Wechsler, D. (2003). The WISC-IV technical and interpretive manual. San Antonio,
TX: Psychological Corporation. 6