Monday, October 01, 2007

DIAL-3 factor study: Alternative CHC interpretation

[Double click on image to enlarge]

A recently published (Journal of School Psychology) article (Anthony et al., 2007; click here to view) reported an independent factor analysis of the Developmental Indicators for the Assessment of Learning--Third Edition (DIAL-3), an instrument designed for use with preschool-aged subjects. The sample was large (n=2000+) and both exploratory and confirmatory factor analysis methods were employed. I believe the study has merit given the sample size and reasonable factor methods employed. Below is the abstract:
  • To examine the convergent and discriminant validity of the scales on the Developmental Indicators for the Assessment of Learning—Third Edition [DIAL-3; Mardell-Czudnowski, C., and Goldenberg, D.S. (1998). Developmental indicators for the assessment of learning—third edition. Circle Pines, MN: American Guidance Service, Inc.], exploratory and confirmatory factor analyses were performed on randomly selected subsamples of 2012 children who attended Head Start. Exploratory factor analysis yielded three factors, labeled Verbal Ability, Nonverbal Ability, and Achievement, which collectively accounted for 56% of the variance in children's performances. Confirmatory factor analysis evaluated this empirically-derived model and the conceptually-derived model of the authors of the DIAL-3 in a separate subsample of children. Although neither model explained the data extremely well, the empirically-derived model characterized children's performances better than the conceptually-derived model, e.g., CFIs=.90 and .85, RMSEAs=.07 and .10, respectively. The discussion highlights an alternative conceptualization of the DIAL-3, potential uses of the factor scores, ideas for consideration during the next revision of the DIAL-3,and the need for additional validity research.
My two cents re: this study is not the number of factors extracted/confirmed (n=3), which seems reasonable, but the interpretation of the factors. The final accepted confirmatory model can be seen in the figure above.

Although the authors reference Carroll's (1993) seminal factor research synthesis and the work of Cattell-Horn to support their factor interpretations, the authors apparently did not attend to the entire work of Carroll. I concur that the factor they label as Verbal could also be interpreted to represent cyrstallized intelligence (Gc). However, the authors "Nonverbal" factor is incorrectly (IMHO) suggested to measure fluid intelligence (Gf). An inspection of the tests that load on the so-called Nonverbal factor reveals tests that are primarily measures of psychomotor abilities (e.g., copying, catching, jump/hop/skip, cutting, building with blocks, etc.). Although Carroll's model did not include psychomotor abilities, he did discuss them in a separate chapter in his book. Recently I wrote about the integration of the psychomotor broad ability domain (Gp) into CHC theory. If any "cognitive" abilities are measured in this so-called Nonverbal ability factor the logical choice would be Gv...not Gf.

Finally....I wish researchers would cease with the continued labeling of a "nonverbal" ability. As I've sermonized previously, there is not such cognitive ability as "nonverbal"....there are abilities (e.g., Gf, Gv, Glr) that can be assessed via nonverbal methods...but nonverbal does not exist as a distinct cognitive ability construct.

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