This is a brief presentation that explains why the WJ IV (and WJ III) GIA IQ score is an appropriate and valid indicator of general intelligence that can be used in possible intellectual disability (ID) determinations

1. I. General intelligence is the central tenant of the 1st Prong of an
intellectual disability (ID) diagnosis (Dx)
II. The WJ IV (and earlier WJ III) is listed in authoritative ID-related
publications as a comprehensive measure of general intelligence
suitable for ID assessment
III. The Cattell-Horn-Carroll (CHC) theory is the consensus taxonomic
model of human intelligence
IV. The WJ IV is the most comprehensive measure of the Cattell-Horn-
Carroll (CHC) model of human intelligence and has been the leader in
CHC intelligence test development since circa 1989
V. Validity evidence provided for the WJ IV (McGrew, LaForte & Schrank,
2014), in the judgement of independent scholars, supports the validity
of the WJ IV GIA as valid indicator of general intelligence
Overview

2. I. General intelligence is the central
tenant of the 1st Prong of ID

3. General intelligence is the central tenant of the 1st Prong of ID
• “Intellectual disability is characterized by significant limitations
both in intellectual functioning and in adaptive behavior as
expressed in conceptual, social and practical adaptive behavior
skills (AAIDD, 2010)
• “Intellectual functioning is currently best captured by a general
factor of intelligence. Intelligence is a general mental ability”
(AAIDD, 2010; p. 31; italics added).
• DSM-5 (APA: DSM-5, 2013) also refers to an intellectual
developmental disorder as requiring “deficits in general mental
abilities (Criterion A)” (p. 37; italics added).

4. • A person’s general intelligence (g) cannot be seen or observed—it is a
latent, unobservable, theoretical construct.
• IQ test scores are the vehicles for operationalizing the theoretical construct
of general intelligence (g) via observable or manifest indicators (tests)
• The total composite IQ score (often called the full scale IQ score) from a
comprehensive IQ test can be considered the best available and practical
proxy of the unobservable (aka., latent; hidden; not observable) factor of
general intelligence—historically referred to as g in the psychological
literature (Gottfredson, 1997; Gottfredson & Saklofske, 2009; Haeir, 2016;
Horton & Reynolds, 2015; Jensen, 1998; Kaufman, 2009; Neisser et al., 1996;
Schneider & Flanagan, 2015; Watson, 2015; Widaman, 2015).
• The full scale IQ score from a comprehensive intelligence battery “is the
best estimate of a person’s general intellectual ability for the purposes of
diagnosing ID” (McGrew, 2015a, p. 87; italics added; also see Tassé &
Blume, 2018).

5. General intelligence cannot
be seen or directly measured.
It is hidden.
Comprehensive IQ tests,
like the WJ IV, WAIS-IV, etc.,
provide practical,
observable vehicles (tests)
from which we infer a
person’s general
intelligence.

6. Jensen & Weng (1994) Latent,
hidden,
unobservable
intelligence
constructs
(theoretical
domain)
Observable,
manifest,
obtained test
score
indicators of
constructs
(measurement
domain)
General intelligence (g)(Note-red material
added to original
figure)

7. WAIS-IV
Full Scale IQ
Latent, hidden,
unobservable
intelligence constructs
(theoretical domain)
Observable,
manifest,
obtained test score
indicators of
general intelligence
(g) construct
(measurement
domain)
SB-V
Full Scale IQ
General
intelligence
(g)
• The full scale IQ score from a comprehensive intelligence battery “is the best
estimate of a person’s general intellectual ability for the purposes of diagnosing
ID” (McGrew, 2015a, p. 87; italics added; also see Tassé & Blume, 2018).
• The Wechsler tests, Stanford-Binet, and Woodcock-Johnson tests are the most
psychometrically sound, individually administered, comprehensive proxies for
general intelligence for adults (two most recent versions of each depicted above).
WAIS-III
Full Scale IQ
SB-IV
Full Scale IQ
WJ IV GIA
IQ score
WJ III GIA
IQ score

8. II. The WJ IV (and earlier WJ III) is
listed in authoritative ID-related
publications as a comprehensive
measure of general intelligence
suitable for ID assessment

9. (2002)

12. Floyd, R. G., Farmer, R. L.,
Schneider, W. J., & McGrew, K. S.
(2018, in press). Theories and
measurement of intelligence. In
L. M. Glidden (Ed.), APA
handbook of intellectual and
developmental disabilities.
Washington, DC: American
Psychological Association.

13. Floyd, R. G., Farmer, R. L., Schneider, W. J., & McGrew, K. S. (2018, in
press). Theories and measurement of intelligence. In L. M. Glidden
(Ed.), APA handbook of intellectual and developmental disabilities.
Washington, DC: American Psychological Association.

14. 2015
From McGrew chapter
on intellectual
functioning

15. 2015
From Watson chapter
on intelligence testing

16. III. The Cattell-Horn-Carroll
(CHC) theory is the consensus
psychometric taxonomic model of
human intelligence

17. “The Cattell–Horn–Carroll (CHC) theory
of cognitive abilities is the best validated
model of human cognitive abilities”
Ackerman, P. L. & Lohman D. F. (2006). Individual differences in
cognitive functions. In P. A. Alexander, P. Winne (Eds.), Handbook of
educational psychology, 2nd edition (pp. 139-161). Mahwah, NJ: Erlbaum.
CHC is the consensus psychometric model of
intelligence

18. “The CHC model provides an excellent fit to a
broad range of individual differences data and is
therefore considered one of the best, if not the best,
latent variable models of intelligence in the
psychometric literature”
CHC is the consensus psychometric model of
intelligence
Conway, A. R., & Kovacs, K. (2015). New and emerging
models of human intelligence. Wiley Interdisciplinary
Reviews: Cognitive Science, 6(5), 419-426.

19. “The CHC model is the most strongly supported,
empirically derived taxonomy of cognitive abilities…and
has influenced the development of most contemporary
intelligence tests”
CHC is the consensus psychometric model of
intelligence
Jewsbury, P. A., Bowden, S. C., & Duff, K. (2017). The Cattell–
Horn–Carroll model of cognition for clinical assessment.
Journal of Psychoeducational Assessment, 35(6), 547-567.

20. “In current psychometric theory, the integration of Cattell
and Horn (1978) model of fluid intelligence with Carroll’s
(1993) 3-stratum model (often referred to as the Cattell-
Horn-Carroll model (CHC) is the dominant model of the
architecture of the human mind”
CHC is the consensus psychometric model of
intelligence
Demetriou, A., Makris, N., Spanoudis, G., Kazi, S., Shayer, M., &
Kazali, E. (2018). Mapping the dimensions of general intelligence:
An integrated differential-developmental theory. Human
Development, 61(1), 4-42.

21. Gc GrwGqGf Gwm Gv Ga Gl Gr Gs Gt
(More ability domains have been identified. Those listed here
are those that are measured [completely or partially] in most
contemporary intelligence tests)
Definitions on next slide
g
Cattell-Horn-Carroll Theory (CHC) of Cognitive Abilities
g

22. Comprehension-knowledge (Gc): The depth and breadth of
declarative and procedural knowledge and skills valued by one’s
culture. Comprehension of language, words, and general
knowledge developed through experience, learning and
acculturation.
Visual-spatial processing (Gv): The ability to use mental imagery,
store images in primary memory, or perform visual-spatial analysis
or mental transformation of images in the “mind’s eye.”
Domain-specific knowledge (Gkn): The depth, breadth, and
mastery of specialized declarative and procedural knowledge
typically acquired through one’s career, hobby, or other passionate
interest. The Gkn domain is likely to contain more narrow abilities
than are currently listed in the CHC model.
Auditory processing (Ga): The ability to perceive, discriminate,
and manipulate sounds and information received through the ears.
Includes the processing of auditory information in primary
memory and/or the activation, restructuring, or retrieval of
information from semantic-lexical memory based on phonemes.
Reading and writing (Grw): The depth and breadth of declarative
and procedural knowledge and skills related to written language or
literacy.
Learning efficiency (Gl): The ability and efficiency to learn, store,
and consolidate new information in long-term memory.
Quantitative knowledge (Gq): The depth and breadth of
declarative and procedural knowledge related to mathematics. The
Gq domain is likely to contain more narrow abilities than are
currently listed in the CHC model.
Retrieval fluency (Gr): The rate and fluency at which individuals
can produce and retrieve verbal and nonverbal information or
ideas stored in long-term memory.
Fluid reasoning (Gf): The use of deliberate and controlled focused
attention to solve novel “on the spot” problems that cannot be
solved solely by using prior knowledge (previously learned habits,
schemas, or scripts). Reasoning that depends minimally on
learning and acculturation.
Processing speed (Gs): The ability to control attention to
automatically and fluently perform relatively simple repetitive
cognitive tasks. Attentional fluency.
Short-term working memory (Gwm): The ability to encode,
maintain, and/or manipulate auditory or visual information in
primary memory (while avoiding distractions) to solve multiple-
step problems. The mind’s mental “scratchpad” or “workbench.”
Reaction and decision speed (Gt): The speed at which very simple
perceptual discriminations or decisions can be made.

23. IV. The WJ IV is the most
comprehensive measure of the
Cattell-Horn-Carroll (CHC) model
of human intelligence and has
been the leader in CHC
intelligence test development since
circa 1989

24. Strong g indicators Moderate g indicators Weak g indicators
GcGf Gv Gwm Ga Gl Gr Gs
g
Gv = Visual-spatial processing
Gwm = Working memory
Ga = Auditory Processing
Gl = Learning efficiency
Gr = Retrieval fluency
Gf = Fluid reasoning (intelligence)
Gc = Comprehension-knowledge
(aka., crystallized intelligence)
Gs = Processing speed
Consensus Cattell-Horn-Carroll (CHC) psychometric model of human intelligence
(only broad ability domains typically represented in IQ tests included in model)
Broad ability
domains
Full scale IQ scores are psychometric measurable estimates of hidden (latent)
construct of general intelligence (g)
Psychometric and theoretical soundness of full scale IQ scores
According to well known psychometric principles, the most optimal IQ scores for representing general intelligence (g) include (a) tests
that sample as great a diversity or variety of CHC ability domains as possible (aka., psychometric sampling error or adequacy) (Carroll,
1993; Jensen, 1987; 1984; 1998), (b) includes a minimum of six tests that samples at least three of the broad ability domains, and (c)
adequately represents the most important CHC abilities that measure complex cognitive functioning

25. Comparison of CHC ability domains represented in the total
composite score for three primary adult tests of general intelligence
Gc GvGwmGf Ga Gl Gr Gs
gg
WJ IV
WAIS-IV
SB-V Squares represent tests

26. WJ IV General Intellectual Ability (GIA) composite score represents
general intelligence (g) – weighted sum of the seven tests
Gc GvGwmGf Ga Gl Gr Gs
g
Tests Number
Series
Oral
Vocabulary
Verbal
Attention
Visual-
ization
Phonological
Processing
Story
Recall
Letter-
Pattern
Matching
GIA

27. V. Validity evidence
provided for the WJ IV
(McGrew, LaForte &
Schrank, 2014), in the
judgement of independent
scholars, supports the
validity of the WJ IV GIA
as valid indicator of
general intelligence (g)

28. WISC-IV WAIS-IV WPPSI-III KABC-II SB-5 DAS-II
FS IQ FS IQ FS IQ FCI FS IQ GCA
(n =174) (n =177) (n = 99) (n=50) (n = 50) (n = 49)
WJ IV g-measures
General Intellectual Ability (GIA) 0.86 0.84 0.72 0.77 0.80 0.83
Brief Intellectual Ability (BIA) 0.83 0.74 0.76 0.79
Gf-Gc Composite 0.83 0.78 0.71 0.82
Note. Correlations in italic represent correlations with a pseudo-WJ IV GIA score computed from 7
WJ IV tests (WJ IV COG does not provide an GIA-Edv cluster)
Select concurrent validity evidence: Correlations of WJ
IV primary COG g-scores with external measures
(McGrew et al., 2014)
Conclusion: The WJ IV GIA, BIA and Gf-Gc composite clusters demonstrate strong validity
evidence as measures of general intelligence when the criterion are the global composite/total
scores from other major IQ batteries in the field

29. Independent
review

30. Independent
review

31. Independent
review

32. Conclusion from
independent peer
reviewed
research

33. I. General intelligence is the central tenant of the 1st Prong of ID
II. The WJ IV (and earlier WJ III) is listed in authoritative ID-related publications as a
comprehensive measure of general intelligence suitable for ID assessment
III. The Cattell-Horn-Carroll (CHC) theory is the consensus taxonomic model of human
intelligence
IV. The WJ IV is the most comprehensive measure of the Cattell-Horn-Carroll (CHC) model
of human intelligence and has been the leader in CHC intelligence test development since
circa 1989
V. Validity evidence provided for the WJ IV (McGrew, LaForte & Schrank, 2014), in the
judgement of independent scholars, supports the validity of the WJ IV GIA as valid
indicator of general intelligence
VI. An individual’s WJ IV GIA score is psychometric sound indicator of general intelligence
and, therefore, should be considered a reliable and valid indicator of general level of
intellectual functioning, for consideration of a possible diagnosis of ID (1st Prong)
Summary