Individual differences in cognition: British contributions over a century

Research on individual differences in mental abilities is discussed from th ree viewpoints: the psychometric structure of ability differences, the pred ictive validity of mental test scores, and some putative causes of psychome tric intelligence differences in terms of psychometric and cognitive compon ents and biological indices. A hierarchical descriptive structure for menta l ability differences, as it emerged in the 1980s and 1990s, prominently di splays British discoveries and suggestions, especially those of Spearman, B urt and P. E. Vernon from the first half of the 20th century. Galton and Sp earman's largely unproductive search for the origins of ability differences has seen new activity since the 1970s, and there are several replicable as sociations that are yet to be explained. Over the 20th century the emphasis has been on measuring mental ability differences; at its beginning there w as an emphasis (largely British) on understanding psychometric intelligence . The new century is likely to see a continuation of this re-emphasis on ex plaining human ability differences.