"Intelligent" intelligence testing with Wechsler Arithmetic test

This article is a good reminder that "intelligent" intelligence testing requires "knowing thy subtests."

The authors conclude "In summary, while Arithmetic may be considered a measure of concentration or working memory, it should be kept in mind that many other factors influence it and that its specificity as a concentration measure is limited."







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Why full scale IQ scores are often much lower (or higher) than the part scores? Dr. Joel Schneider on the "composite score extremity effect"

Bingo.  There is finally an excellent, relatively brief, explanation of the phenomena of why full scale IQ scores often diverge markedly from the arithmetic average of the component index or subtest scores.

This composite score extremity effect (Schneider, 2016)  has been well known by users of the WJ batteries.  Why....because the WJ has placed the global IQ composite and the individual tests on the same scale (M=100; SD=15).  In contrast, most other cognitive ability batteries (e.g., Wechslers) have the individual test scores on a different scale (M=10; SD=3).  The use of different scales has hidden this statistical score effect from users.  It has always been present.  I have written about this many times.  One can revisit my latest post on this issue here.

Now that the WISC-V measures a broader array of cognitive abilities (e.g., 5 index scores), users have been asking the same "why does the total IQ score not equal the average of the index scores?"  Why?  Because the five index scores are on the same scale as the full scale IQ score...and thus this composite score extremity effect is not hidden.  A recent thread on the NASP Community Exchange provides examples of psychologists wondering about this funky test score issue (click here to read).

As per usual, Dr. Schneider has provided intuitive explanations of this score effect, and for those who want more, extremely well written technical explanations.

The WJ IV ASB 7 can be downloaded by clicking here.  Although written in the context of the WJ IV, this ASB is relevant to all intelligence test batteries that provide a global IQ score that is the sum of part scores.

Kudos to Dr. Schneider.

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New Wechsler Flynn Effect study by Weiss et al. (2015)

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WISC-V expanded index scores: Verbal Expanded Crystallized (Gc) and Expanded Fluid (Gf) index scores and tables

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Somehow I seemed to have missed this development on my research literature monitoring radar.  More comments and a link to the technical report can be found at Joel Schneider's excellent blog.

WAIS-IV US/Canadian norms controversy---articles for readers to review

I previously provided an FYI post on a hot topic in Canada...claims that the new WAIS-IV Canadian norms were flawed.  There are now three articles outlining the different arguments.  The three articles, published in JPA, can be found here, here, and here.

I continue to not comment on this controversy given my obvious conflict of interest as a coauthor of the competing WJ-IV.

Kevin McGrew

WJ IV update: Correlations of WJ IV COG g-scores (GIA,Brief,Gf-Gc composite) and WISC-IV/WAIS-IV FS and GAI IQ scores

In the WJ IV technical manual (McGrew, LaForte, Schrank, 2014) concurrent validity results are presented for the WJ IV COG with the WISC-IV and WAIS-IV (click here for WJ IV COG overview and select correlation information from tech. manual).

A number of psychologists have asked about correlations between the primary WJ IV COG g-scores and the Wechsler General Ability Index (GAI).  They are not presented in the technical manual.  I have now computed those correlations, as well as a few others with the Wechsler GAI, and they are now part of the SlideShare at the link above and are also reported below.  Click on image to enlarge.

Dissertation Dish: Cognitive efficiency (Gsm+Gs) trait stability across time: Scores can and will change

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Is the WAIS-IV factor structure the same in samples of people with ID/MR? This article says "yes"

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IQ score differences across time may relfect real changes in the brain

Lay people and many professionals often express consternation when an individuals measured IQ scores are different at different times in their life.  This concern is particularly heightened in high stakes settings where differences in IQ scores can result in changes in eligibility for programs (e.g., social security disability income) or life-or-death decisions (e.g., Atkins MR/ID death penalty cases).

Factors contributing to significant IQ score differences are many (McGrew, in press a) and may include: (a) procedural or test administration errors (e.g., scoring errors; improper nonstandardized test administration; malingering; age vs. grade norms; practice effects), (b) test norm or standardization differences (e.g., norm obsolescence or the Flynn Effect; McGrew, in press b), (c) content differences across different test batteries or between different editions of the same battery, or (d) variations in a person’s performance on different occasions.

 An article "in press" (Neuroimage) by Burgaleta et al. (click here to view copy with annotated comments)  provides the important reminder that differences in IQ scores for an individual (across time) may be due to real changes in general intelligence related to real changes in brain development.  These researchers found that changes in cortical brain thickness were related to changes in IQ scores.  They concluded that "the dynamic nature of intelligence-brain relations...support the idea that changes in IQ across development can reflect meaningful general cognitive ability changes and have a neuroanatomical substrate" (viz., changes in cortical thickness in key brain regions).  The hypothesis was offered that changes in the the cortical areas of  frontoparietal brain network (see P-FIT model of intelligence) may be related to changes in working memory, which in turn has been strongly associated with general reasoning (fluid intelligence; Gf).

The cortical thickness-IQ change relation was deemed consistent with "cellular events that are sensitive to postnatal development and experience."  Possible causal factors suggested included insufficient education or social stimulation during sensitive developmental periods, as well as lifestyle, diet and nutrition, and genetic factors.

• McGrew, K. S. (in press a).  Intellectual functioning:  Conceptual issues.  In E. Polloway (Ed.), Determining intellectual disability in the courts:  Focus on capital cases.  AAIDD, Washington, DC.

•  McGrew, K. S. (in press b).  Norm obsolescence:  The Flynn Effect.  In E. Polloway (Ed.), Determining intellectual disability in the courts:  Focus on capital cases.  AAIDD, Washington, DC.

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The Wechsler Arithmetic subtest measures quantitative reasoning...another study

A new study on the now "old" WISC-III which still provides insights into the debate regarding what the Wechsler Arithmetic subtest measures. Consistent with research I have coauthored and my analysis of other studies (click here to view), this new study is consistent with the classification of Arithmetic as primarily a measure of quantitative reasoning.

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Factor structure of the WAIS-IV/WMS-IV: A CHC interpretation

A nice cross-battery CFA of the WAIS-IV and WMS-IV. Also, this article provides a nice historical overview of the changes of the two linked batteries over time. [Click on images to enlarge].

I would put a CHC theory spin on the validated factors. Verbal Comp = Gc; Perceptual Reasoning (Gf/Gv blend); Working Memory (Gsm...or what I know think should be labeled Gwm); Processing Speed (Gs), and Delayed Memory (Glr).











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Special JPA issue on Wechsler intelligence batteries

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Research Byte: CHC and convergence in cognitive assessment

 

 

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Research Byte: Structural and incremental validity of WAIS-IV

 

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Research Byte: Which is better measure of intelligence? WAIS-III or WAIS-IV

A new article comparing the changes from the WAIS-III to the WAIS-IV with implications for Atkins cases by Taub and Benson. Below is the abstract. Dr. Taub can be contacted via this link.

A previous IAP AP101 report dealing with WAIS-III/WAIS-IV structural changes is worth reading when reviewing this current article.

 

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Historical review of WISC to WISC-IV

This article is an open access article and thus I am providing a link to a copy.

The article helps users understand the various changes that have occurred in this series, changes which may help explain IQ score differences in individuals who may have taken various versions over time.

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Research byte: WAIS-IV Visual Puzzles study

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Roberts et al (2005) on Wechslers, WJ III and CHC theory

From the above excellent book. See select comments about the Wechslers, WJ III and CHC theory by Roberts et al. - a very good chapter in an excellent book.



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Research byte: Practice effects on neuropsych and IQ measures: Meta-analysis

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CHC theory and the Wechsler IQ scales and test development and interpretation

In 1998 Dr. Dawn Flanagan and I published the Intelligence Test Desk Reference book which was the first thorough treatment of CHC theory (then called Extended Gf-Gc theory). This book is now out-of-print.




We then took the concepts from the ITDR and, together with Dr. Sam Ortiz, presented a cross-battery approach to interpreting the Wechsler batteries.




And again, this book is no longer in print. This also means we no longer receive any $ for sales (conflict of interest disclosure). Table of contents for first three chapters below (click on images to enlarge)






The research, theory, and conceptual material in the second book is nearly identical to the first, but it was presented in the context of how to upgrade interpretation and understanding of the Wechsler batteries according to the CHC framework. Since then the same CHC overview material has been tweaked and updated in a series of CHC cross-battery books by Flanagan et al. But, the foundation of CHC theory, and how it can be integrated within a conceptual framework of test development and interpretation, is largely the same in these newer CHC cross-battery books.

Thus, given that these "mother and father" books are no longer in print, I took the liberty of copying the first three chapters of the Wechsler oriented book and am now making them available for my readers (click here). I make this material available to provide psychologists who have not done much reading regarding CHC theory an opportunity to have access to the basic foundation of CHC theory to help them see how it can be applied to the interpretation of an intelligence battery (in this case the Wechslers). By choosing the Wechsler material this also helps understand how the Wechsler batteries are evolving (either implicitly or explicitly--see Keith and Reynolds, 2010) when viewed from the lens of CHC theory.

But, one must recognize that this material is a bit dated. An update of CHC theory was later published in 2005 (click here to access...plus some other chapters), and was again updated this year by Schneider and McGrew (click here).

However, the CHC chapter I provide in this blog post, particularly when placed in the context of the Wechsler batteries, provides a solid foundation for understanding CHC theory and its impact on contemporary intelligence test development and interpretation. My goal is to increase awareness of CHC theory and its relevance to psychological assessment and interpretation. My goal is to spur others to become more current re: this now dominant framework in the field of applied IQ testing.


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