“I should point out that a number of factor analytic studies of Piagetian tests along with other measures commit an egregious psychological error by orthogonally rotating the factors (or principal components) by some method such as varimax, which prohibits the emergence of the large general factor in all such tests. About the only wholly correct factor analysis of Piagetian tests I have found in the literature is the one by Philip Vernon (1965), a well-known expert in factor analysis and psychometrics. Many developmental psychologists, with no special training in factor analysis or psychometrics, simply select the most popular computer program, Kaiser’s varimax, for doing their factor analyses. As applied to factor extraction in the abilities domain, this is flatly wrong, not mathemati­cally, but psychologically and scientifically. In the abilities domain, either oblique rota­tion should be done to permit the hierarchical extraction of g, or the g factor should be extracted (as the first principal factor) prior to rotation of the remaining factors. (In the latter procedure, one additional factor should be extracted prior to rotation.) It will be a great day for psychology when we no longer have to read studies in which the author automatically applies the varimax computer program (which is expressly intended to “ rotate away” a general factor) and then points out that “ factor analysis” fails to reveal a general factor in his test data!”

Arthur Jensen, Bias in Mental Testing, p. 675.

And yet we see things such as this: http://ing.dk/artikel/135473-intelligens-er-mange-ting-bare-ikke-ven-med-alderen

which is about the study: – Hampshire, A., Highfield, R., Parkin, B., and Owen, A. (2012). ‘Fractionating Human Intelligence Neuron’, 76 (6), 1225-1237, DOI: 10.1016/j.neuron.2012.06.022

The study even cites SJ Gould as an authority on testing. How retarded is that. I can’t imagine they actually read the Carroll book they cited (1993), because then they should know some more about factor analysis. Groan