Organizational Models

As the search for distinct intellectual factors progressed, their number multiplied,
and so did the number of models devised to organize them. One
type of scheme, used by Cyril Burt, Philip Vernon, and others, is a hierarchical
arrangement of factors. In these models, Spearman’s g factor is placed at
the top of a pyramid, and the specific factors are placed at the bottom. In between,
there are one or more levels of group factors selected in terms of
their breadth and arranged according to their interrelationships with the
more general factors above them and the more specific factors below them.
In Vernon’s scheme, for example, the ability to change a tire might be
classified as a specific factor at the base of the pyramid, located underneath
an intermediate group factor labeled mechanical information, which in
turn would be under one of the two major group factors identified by
Vernon as the main subdivisions under g —namely, the practical-mechanical
factor. The hierarchical scheme for organizing mental abilities is a useful device
that is endorsed by many psychologists on both sides of the Atlantic
Ocean. It recognizes that very few tasks are so simple as to require a single
skill for successful performance, that many intellectual functions have some
common elements, and that some abilities play a more pivotal role than others
in the performance of culturally valued activities.

Another well-known scheme for organizing intellectual traits is the
structure-of-intellect (SOI) model developed by J. P. Guilford. Although the
SOI is grounded in extensive factor-analytic research conducted by Guilford
throughout the 1940’s and 1950’s, the model goes beyond factor analysis
and is perhaps the most ambitious attempt to classify systematically all the
possible functions of the human intellect. The SOI classifies intellectual
traits along three dimensions—namely, five types of operations, four types
of contents, and six types of productions, for a total of 120 categories
(5 × 4 × 6). Intellectual operations consist of what a person actually does (for
example, evaluating or remembering something), the contents are the
types of materials or information on which the operations are performed
(for example, symbols, such as letters or numbers), and the products are the
form in which the contents are processed (for example, units or relations).

Not all the 120 categories in Guilford’s complex model have been used, but
enough factors have been identified to account for about 100 of them, and
some have proved very useful in labeling and understanding the skills that
tests measure. Furthermore, Guilford’s model has served to call attention to
some dimensions of intellectual activity, such as creativity and interpersonal
skills, that had been neglected previously. 454