Playing statistical ouija board with commonality analysis: good questions, wrong assumptions

Commonality analysis, as used by Hale, Fiorello, and colleagues (e.g., Hale, J. B., Fiorello, C. A., Kavanagh, J. A., Holdnack, J. A., & Aloe, A. M. [2007]. Is the demise of IQ interpretation justified? A response to special issue authors. Applied Neuropsychology, 21, 37-51), often leads to unjustified conclusions. Analyses of simulated datasets show that the highest-order commonality is a poor operationalization of the general factor of intelligence (g). Under commonly observed conditions, it is plausible that lower-order commonalities and unique components in a commonality analysis can consist entirely of g. Other problems with Hale and colleagues' (2007) analyses and interpretations are also discussed.