1. 1. Introduction
The Cattell-Horn-Carroll (CHC) Theory of Cognitive Abilities:
Past, Present and Future

Kevin S. McGrew
University of Minnesota

One of the most successful undertakings attributed to modern psychology is the measurement of mental abilities. Though rarely appreciated outside academe, the breakthrough in objectively gauging the nature and range of mental abilities is a pivotal development in the behavioral sciences. While this accomplishment has far-  reaching implications for many areas of society, the full meaning of the test data has lacked a comprehensive theory that accounts for several major developments over the years. The track of data left by researchers remains diffuse without a clear signpost in the broad landscape of mental abilities........Lamb, 1994

Since the beginning of our existence, humans have searched for order in their world. Today classification is an “activity that is essential to all scientific work” (Dunn & Everitt, 1982).  The reliable and valid classification of entities, and research regarding these entitites and newly proposed entities, requires a “guide” or taxonomy (Bayley, 1984; Prentky, 1994). Although Lamb’s (1994) lament about the lack of a clear signpost in the broad landscape of mental abilities had been true for decades, the crystallization of an empirically-based psychometric taxonomy of human cognitive abilities finally occurred in the late 1980’s to early 1990’s.
In 1997, it was predicted that progress in intelligence testing was being, and would continue to be energized, as a result of the articulation of this new consensus taxonomy of human cognitive abilities.  The detailed description and articulation of the psychometric “table of human cognitive elements” in John “Jack” Carroll’s (1993) Human cognitive abilities: A survey of factor- analytic studies, which concluded that the Cattell-Horn Gf-Gc theory was the most empirically grounded available psychometric theory of intelligence, resulted in McGrew (1997) recommending that “all scholars, test developers, and users of intelligence tests need to become familiar with Carroll’s treatise on the factors of human abilities” (p. 151).   It was further suggested that practitioners heed Carroll’s suggestion to “use his ‘map’ of known cognitive abilities to guide their selection and interpretation of tests in intelligence batteries” (p. 151).   It was the purpose of the chapter to contribute, albeit in a small way, to the building of “a ‘bridge’ between the theoretical and empirical research on the factors of intelligence and the development and interpretation of psychoeducational assessment batteries” (p. 151).
     This current document continues to focus on the construction of the theory-to-practice bridge, a bridge grounded in the Cattell- Horn-Carroll (CHC) theory of cognitive abilities.  The primary goals of this document are to: (1) describe the evolution of contemporary CHC theory, (2) describe the broad and narrow CHC abilities, including, where appropriate, the integration of factor analytic research (since 1993) that suggests possible refinements to the taxonomy, and (3) review structural evidence that supports the broad strokes of CHC theory.