Monday, October 20, 2008

WJ III: 2-D MDS analysis ages 6-18

As promised, this is a follow-up to my posting of a 3-D Guttman Radex MDS model of WJ III tests. I'm now presenting a 2-D Radex model based on the analysis of all WJ III norm subjects from ages 6-18 (using the WJ III NU norms). You can view/download the pdf file by clicking here.

I could write an entire chapter on implications, hypotheses, etc. Instead, I'm going to make just a few comments and post a few questions in hopes that this approach to examining the characteristics of tests generates some interest. IMHO, MDS is an excellent analytic tool that provides a unique lens by which to augment our factor-analytic based understanding of cognitive ability tests. I wish more of us would complete these analyses with all major intelligence batteries.

A few thoughts/comments/questions:
  • Note that Concept Formation is near the middle of the circle. This whole round of MDS analyses I've been posting is based on a concern (see J. Schneider comments) whether the CF test was a good measure of Gf....and if it was strongly related to g. As per MDS interpretation, the proximity of CF to the middle cross-hairs suggests it is one of the more "cognitively complex" tests in the entire WJ III battery. This would support its interpretation as a strong indicator of Gf and g.
  • Notice that Sound Awareness (Ga/Gsm), Understanding Directions (Gsm/Gc), Applied Problems (Gq/Gf), Quantiative Concepts (Gq/Gf), and Verbal Comprehension (Gc) are also close to the middle - suggesting that they are all cognitively demanding measures in terms of the concept of cogntive complexity. And...interestingly they come from different CHC broad factors. I'm convinced that the reason Sound Awareness and Understanding Directions are cognitively complex is the major working memory load placed on subjects during these tasks. This should serve to remind us that cognitive complexity does NOT necessarily need to be associated with abstract "thinking" (Gf-ish) type tasks. Further notice that Auditory Working Memory is not that far away either. Do these findings support the research that suggest a strong relation between working memory (Gsm-MW) and Gf or g?
  • Notice how "tight" or "cohesive" some of the respective CHC factor tests are. Clearly the Grw, Gq, Gc, Gf, and Gsm (except for MS) tests all tend to hang in the same proximity. In contrast notice the wide degree of distance between the WJ III Gv and Ga tests. Does this suggest that some broad CHC domains are more tight/cohesive while other domains are much broader (lower domain cohesion). What does this mean for test interpretation? What does this mean for understanding the theoretical nature of the different CHC factor domains?
  • Notice the cool cognitive efficency (CE) quandrant. Isn't it sweet how most all the Gs and Gsm tests can be circumscribed in one area. Yet...there is distance between the CE tsts which probably is very informative in understanding differences in the characteristic process/content demands placed on subjects. Isn't this exciting?
  • Is the fact that most Gv tests are far from the cognitive complexity center (as were most of the Wechsler Gv tests in the enclosed slide in the file) helping us understand why traditonal Gv tests are repeatedly found to be unrelated (statistically) to school achievement (esp. mathematics), when we know that considerable research indicates that Gv is important for mathematics. Does this tell us that we have yet, in the world of applied test development, failed to develop sufficiency complex and cognitively demanding Gv tests that would relate more to school achievement (e.g., visual-spatial working memory tests). Curious minds want to know.
  • Like Gv, notice the distances between the Ga tests (which do form a nice psychometric factor when using traditonal factor methods). Incomplete Words is quite far away from Sound Blending, which in turn is closer to the acquired knowledge tests. Does this suggest that IW may be the more "pure" phonetic coding measure while SB is potentially influenced by training and education? Further note the location of Auditory Attention --- I've included it among the cognitive efficiency area. Is this telling us that the sound discrimination (Ga component) of the AA test is minimal while the selective attention (under distraction--ability to resist distractions) component is greater?
  • I'm not comfortable with the interpretation of quandrant 4 in the model. Can others suggest ideas? I think part of the problem is that a 3-D model (like the one I posted the other day) may required to better account for the dimensionality of the complete set of WJ III tests.
I could stare at this forever and generate more thoughts, hypotheses, questions, etc. I'd like to leave that to others. Please feel free to start a thread discussing the potential benefits of examing cognitive and achievement tests via the lens of MDS analysis. It clearly is an under-utilized methodology that can help us better understand our measures. A problem is that most quantoids (myself include) have become seduced by the more sexy contemporary SEM (CFA) methods. Maybe it is time we go "back to the future."

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