ABSTRACT
Introduction Chapter 8 made some rather important points. It indicated that almost all human abilities are positively correlated together and that it is possible to describe these correlations either by a single factor of general ability (as suggested by Spearman), by a set of 20 or more ‘primary mental abilities’ (as suggested by Thurstone), by a few ‘group factors’ (as suggested by Burt and Vernon) or, most generally, by a hierarchical model that incorporates all of these features (as suggested by Carroll, Cattell and Gustafsson). This really is quite interesting. It would logically be quite possible for human abilities to be independent of each other – after all, why should abilities as diverse as musical talent, mathematical skill, vocabulary, memory or ability to visualize shapes be interrelated? It is not as if there are any obvious processes (e.g. pieces of knowledge or skills taught through education) that are common to all of them and that could, therefore, account for their interrelationships.
