Primary Mental Abilities
As soon as the methods of multiple-factor analysis had been developed to the point where practical application seemed feasible, we started work on such a project. The development of a large battery of fifty-seven tests for various aspects of intelligence was a large undertaking. When this job had been done, the whole battery was given to a group of 240 volunteers in the spring of 1934. Analysis of these records constituted our first attempt to identify primary mental abilities. A short paper on this experiment was published in Psychometrika[29]and a more complete report constituted the first issue in the Psychometric Monograph Series.[30]Although my first text on multiple-factor analysis, The Vectors of Mind, had previously been published (1935), with a development of the concepts of communality, the rotation of axes, and the use of oblique axes, I hesitated to introduce all of these things in the first experimental study. In particular, there was strong advice from Thorndike, Kelly, and other men for whom I had respect, that an oblique reference frame would be completely unacceptable. Instead of proceeding according to my convictions, that first factor study was published with the best fitting orthogonal frame, although we knew about more complete methods. This was an effort to avoid the storm of controversy that we feared in the introduction of so many different procedures in the first experimental study.
In the last fifteen years the identification of primary abilities and traits has proceeded at an entirely unexpected pace. Fortunately the problem has attracted the attention of some mathematicians and mathematical statisticians. A number of the papers are so technical that they are beyond the comprehension of some of the rest of us who were concerned with the development of these methods in their primitive stage.
The correlations of the primary factors can be factored, just like the correlations among tests. When this is done we find several second-order factors. One of these seems to agree very well with Spearman's general intellective factor g. The critics feature our support of Spearman's g, but they ignore the fact that this work represents at least a modest gain in unraveling the complexities of mental organization.