Thursday, March 02, 2006

Executive function, Gf and Gc - a WAIS CFA study

Another great post over on the Developing Intelligence blog re: executive functioning (EF), this time an empirical study that investigated the relations between components of EF and indicators of Gf and Gc as measured by select WAIS-III tests and the Ravens Progressive Matrices. DI provides a link to the study abstract. To augment the DI post, I've posted a copy of the original Psychological Science article for those that want "the rest of the stofy" (click here).

As most CHC folks would predict, I do have one methodological bone to pick with the study. Gf is defined by the Ravens (good choice) and WAIS-III Block Design. As we all know from contemporary CHC-based CFA studies, and Carroll's seminal treatise on human cognitive abilities, Block Design is primarily an excellent indicator of Gv (Visualization and/or Spatial Relations) and is NOT an indicator of Gf. If it includes any Gf variance, it is small. Thus, the Gf construct in this study is confounded with Gv abilities. Take the Gf-EF findings with a grain of construct-irrelevant variance salt.

As summarized at DI (go to DI link above for complete discussion at DI - italics below added by me).
  • Structural equation modeling confirmed that updating is of particular importance to the correlations between Gc, Gf, and WAIS IQ (which all shared 41 to 48% of their variance with updating). However, once this variance was included as a common underlying factor between the intelligence measures, the correlations with the other two EF subfunctions was no longer significant. This critical finding suggests that shifting and inhibition contribute to intelligence measures only insofar as they covary with updating abilities.

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