Tuesday, July 27, 2010

Joint CFA (Floyd et al., 2010) of WJ III and DKEFS: Guest comments by John Garruto

John Garruto took advantage of my offer and thus, now provides his comments regarding the following recently published research study.  John has been a regular guest blogger at IQ's Corner....how about the rest of you!!!!!!! 

I am open to any topic, but am particularly interested in guest posts regarding articles that have been FYI-mentioned at this blog (typically under Research Bytes tag)---and I especially would like to encourage graduate students to send me possible guest posts...as a way to get experience with analyzing research and providing brief summaries.  Maybe some of my professorial colleagues could make the submission of one guest blog post a requirement in one of their classes :)
  • Floyd, R. G., Bergeron, R., Hamilton, G. & Parra, G. R. (2010).  How do executive functions fit with the Cattell-Horn-Carroll model? Some evidence from a joint factor analysis of the Delis-Kaplan Executive Function System and the Woodcock-Johnson III tests of cognitive abilities.  Psychology in the Schools, 47(7), 721-738. (click here to view/read)
[Note...these are John's comments with only minor copy editing by the blogmaster/dictator]

Before I go into some thoughts regarding the article by Floyd, Bergeron, Hamilton, and Parra, please bear a bit of a sidetracking set of thoughts that are relevant to this article.  When I was in my masters training program for school psychology, we took a course called “Analysis of Individual Learning I”.  My textbook was authored by Samuel Kirk and James Chalfant (copyright was 1984).  I don’t remember being asked to read anything from that text and it wasn’t until well after I graduated that I learned Samuel Kirk was the person who coined the term “learning disability.” I pulled the book of my shelf and decided to take a look at it.  Chapter 3 is entitled “Causes and contributing factors”.  The entire chapter (which wasn’t long…13 pages) was devoted to the brain and neuropsychology. 

Since that book was published, the law and professional opinion have differed  much on what learning disabilities are.  For years, the psychometric framework has seemingly reigned supreme, using a discrepancy approach and an intuitive paradigm (if the child isn’t working to ability, something must be getting in the way).  For the past six years, RTI has permeated the field of LD with an even more distant framework that Kirk conceptualized…that a learning disability is the failure of a child to respond to research based instruction.  Unfortunately, the brain has largely been left out, with a few exceptions. 

Fortunately, there has been hope.  We’re now seeing a surge in publications that are coauthored by those schooled in both the psychometric and neuropsychological traditions.  They’re not distinct entities-they’re two sides to the same coin (or perhaps “face of the die” is more appropriate).  I remember when I first dove into CHC theory after trying the WJ-III (sadly my program did not use any Woodcock tests in our training)-a paradigm altering notion was that cognition and achievement were not distinct constructs-they were on the same continuum.  This marriage of the psychometric and neuropsychological traditions is happening in the same manner.

This brings us to the article, which has examined ways to categorize executive functions under CHC theory.  The authors performed joint-factor analyses of tests from the WJ-III and Delis-Kaplan Executive Function System (DKEFS).  I initially stopped myself from reading the article and made my guesses.  I scratched down “Retrieval Fluency-Verbal Fluency”, “Concept Formation-Sorting Test”, “Tower-Planning/Spatial Relations”.  “Verbal Comprehension-Word Context”.  I then wrote “Ga-nothing” and “Gsm-nothing”.  These were the subtests that I hypothesized would be grouped together given the nature of their tasks.  Some of the results of this study confirmed my hypotheses and some were not close.

The results presented a six first-order factor model conceptualized under the CHC hierarchy.  The factors included Crystallized Ability (Gc), Processing Speed (Gs), Long Term Storage and Retrieval (Glr), Short-Term Memory (Gsm), Executive Functioning, and Visual-Spatial Processing (Gv).  The groupings were Gc: (DKEFS-Free Sorting, Sort Recognition, Word Context; WJ-III-Verbal Comprehension, General Information); Gs: (DKEFS-Color Word Interference-Inhibition; WJ-III-Visual Matching, Pair Cancellation, Decision Speed); Glr: (DKEFS-Verbal Fluency, Trails switching; WJ-III-Retrieval Fluency, Rapid Picture Naming); Gsm: (DKEFS-Trails switching; WJ-III-Numbers Reversed, AWM, Mem for Words); EF: (DKEFS-Verbal Fluency Switching, Design Fluency Switching; WJ-III Rapid Picture Naming, Concept Formation) and Gv: (WJ-III-Planning, Spatial Relations, Picture Recognition). 

The following were huge surprises for me:

  • Sorting as a measure of Gc…I always saw this test as more of a Gf task (although if one thinks about it-Similarities is a Gc task (with some Gf-ness) even if it hasn’t panned out in some analyses)
  • Tower not having a Gv load
  • Trails not having any Gs variance
  • Concept formation as mental flexibility.  I absolutely see it-but more as hypothesis testing rather than set shifting.  I would have thought Gf and sorting would have “hung” together-perhaps perhaps the verbal sorts must have had an influence?
One cannot read the research of Dr. Floyd and not appreciate his contributions to research on the general factor.  His findings are not only interesting but also important.  He noted that although the strongest loaders on the general factors were from the WJ-III, the DKEFS had more subtests that loaded strongly on the general factor.  This is important as many of us tend to think of EF as regulation of thinking--but clearly there is a higher order ability to EF.  In fact, of the six factors, EF was number two (Gc number one) for ranking of an overall g load. 

Floyd and colleagues did address some of the same musings I had-identifying that sorting and 20 questions are probably better measures of Gf but not word context.  I see word context as also having a Gf nature to it (deductive reasoning).  One must engage in hypothesis testing and construct a mental Venn diagram-the key word must fit all clues.  Perhaps we’re looking at a hybrid of Gf-Gc (could Raymond Cattell be trying to tell us something?) 

Nevertheless, the importance of this article cannot be underscored enough.  There are many skills tapped by EF tests that can impact school performance.  How well would we expect a student who has trouble set-shifting to do on calculations with mixed operations (set-shifting constantly being tapped)-or even long division (requiring three sequential operations for each place value of the quotient).  Also, we can see that tests that review some aspects of neuropsychological performance fit very well within CHC theory. 
I’d like to share one more memory.  I once performed  an evaluation of a a student with TBI that was returning to school. The case highlighted the importance of the ongoing fusion of psychometric and neuropsychological traditions.  The hospital indicated that a WISC and WIAT would be fine (that’s rarely fine for me though!)  I decided to accompany the evaluation with VAL, Retrieval Fluency, and Rapid Picture naming from the WJ-III.  For the latter two, the student said, “I did tasks like these at the hospital.”  Indeed.

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