Kamphaus, 1993; Neisser et al., 1996; Sternberg
et al., 2005). Over the years, there has been no
shortage of either theories or controversies. We
present only a brief overview of several leading
theories here.
Factor Analytic Approaches. Spearman (1927),
the father of factor analysis, posited the existence of
agfactor (general intelligence) andsfactors (specific
intelligence). The elements that tests have in com-
mon are represented byg, whereas the elements
unique to a given test aresfactors. Basically, how-
ever, Spearman’s message, buttressed by factor ana-
lytic evidence, was that intelligence is a broad,
generalized entity.
A number of individuals took issue with Spear-
man’s contentions, including E. L. Thorndike and
L. L. Thurstone. For example, Thurstone (1938)
presented evidence (based on a factor analysis of
over 50 separate tests that had been administered
to 240 participants) for a series of“group”factors
rather than the almightygfactor. Ultimately, Thur-
stone described seven group factors, which he
labeled Numerical Facility, Word Fluency, Verbal
Comprehension, Perceptual Speed, Spatial Visuali-
zation, Reasoning, and Associative Memory (Thur-
stone’s Primary Mental Abilities). Unfortunately,
Spearman and Thurstone were using different
methods of factor extraction (principal components
vs. principal factors) and rotation, which often result
in different solutions even when applied to the
same data set (Gould, 1981). It is also possible that
the discrepant results were due to Spearman analyz-
ing data from a wider range of cognitive ability
levels (i.e., school children) while Thurstone relied
more on data gathered from high cognitive ability
students (i.e., those from a select academic institu-
tion) (Hunt, 2011). Further, both men appeared to
be guilty of reifying the factor(s)“discovered”by
their respective analyses. The end result was an at
times acrimonious debate between Spearman and
Thurstone and their respective followers.Cattell’s Theory. The work of R. B. Cattell
(1987) emphasized the centrality ofg.Atthesame
time, Cattell offered a tentative list of 17 primary
ability concepts. He described two important
second-order factors that seem to represent a parti-
tioning of Spearman’sginto two components:fluid
ability (the person’s genetically based intellectual
capacity) andcrystallized ability(the capacities, tapped
by the usual standardized intelligence test, that can
be attributed to culture-based learning). Essentially,
Cattell’s approach might be described as a hierarchi-
cal model of intelligence. An example of this sort of
model is shown schematically in Figure 7-2.Guilford’s Classification. The views of Guilford
(1967) were quite different from those of Cattell,
Spearman, Thurstone, and most other psychome-
tricians. Guilford proposed aStructure of the Intellect
(SOI) modeland then used a variety of statistical andMajor
group
factors
Minor
group
factors
Specific
factors
Verbal Number informationMechanicalSpatial Manual FiguralVerbal-educational (v:ed) Practical (k:m)General (g)F I G U R E 7-2 Model of a hierarchical organization of abilities.
SOURCE: Adapted fromThe Structure of Human Abilities, rev. ed., by P. E. Vernon, p. 22. Copyright © 1960 by Methuen & Co., Ltd. Reprinted by permission
of Thomson Publishing Services.
198 CHAPTER 7