The structure of intellect (SI) model of intelligence, described in this entry was developed by J. P. Guilford and his associates in the Psychological Laboratory at the University of Southern California. Guilford disagreed with the makers of the major intelligence tests that intelligence was one broad unitary ability. Guilford defined intelligence as a collection of abilities for processing different kinds of information in a variety of ways. Using factor analysis to isolate various components of intelligence eventually led to a three-dimensional model of intellectual abilities called the structure of intellect (SI). Guilford's SI model extended Louis Thurstone's theory of 7 primary abilities of intelligence, into 120 separate components or factors. [Page 837]The three dimensions (operations, content, and products) of the SI model form the various ...