284 THE MISMEASURE OF MANdimensionality and trading some loss of information for the rec-
ognition of ordered structure in fewer dimensions. As a tool for
simplification, it has proved its great value in many disciplines. But
many factorists have gone beyond simplification, and tried to
define factors as causal entities. This error of reification has
plagued the technique since its inception. It was "present at the
creation" since Spearman invented factor analysis to study the cor-
relation matrix of mental tests and then reified his principal com-
ponent asg or innate, general intelligence. Factor analysis may help
us to understand causes by directing us to information beyond the6 • 6 A principal components analysis of four mental tests. All correla-
tions are high and the first principal component, Spearman's g, expresses
the overall correlation. But the group factors for verbal and mathematical
aptitude are not well resolved in this style of analysis.