British psychologist Charles Spearman proposed a conception of intelligence perhaps most widely (though by no means universally) accepted by authors and users of intelligence tests. This chapter discusses Cattell and Horn's Gf-Gc Model, Carroll's Three-Stratum hierarchy, integration of Horn-Cattell and Carroll models to form CHC theory and applications of CHC Theory-Cross-Battery Assessment and Test Development. Stanovich argues for separating mental abilities measured by intelligence tests (MAMBIT) from other abilities, such as rational decision making, Sternberg's three components of successful intelligence, and Gardner's eight intelligences. Factor-based theories of intelligence have proliferated since Spearman started the ball rolling more than a century ago. The time has come for developers of individual clinical tests of intelligence to broaden their basis of test construction beyond the analytic dimension of Sternberg's triarchic theory and to begin to embrace the assessment of both practical intelligence and creativity.

This chapter discusses measuring of intelligence by Francis Galton, J. McK. Cattell, and Alfred Binet. Charles Spearman abhorred the program that would separate the mind into a loose confederation of independent faculties of learning, memory and attention. Although most intelligence researchers today probably accept that the general factor is to stay, they remain sharply divided on its explanation. These disagreements go well beyond a rejection of Spearman's specific suggestions that g is either mental energy or the eduction of relations and correlates. Spearman saw that he needed to provide a psychological or (better still) a neurobiological explanation of g. The two favorite paradigms for this program of research were inspection time (IT) and choice reaction time (RT). Aided by the new technologies of brain imaging, research on intelligence, working memory, and other so-called executive functions has begun to point to some of the brain structures common to them all.