This study focuses on three issues which have been recurrent in the literature on intelligence during the last century: general intellectual capacity; the g factor; and how to influence the development of intelligence. The topics range from neuropsychology to intelligence, personality and information processing. Contributions by scholars from Canada, Europe and the United States are included, representing diverse view points in the field of research into the g factor and into the possibility of raising a person's level of intelligence. The first chapter provides an in-depth summary of research into differences between black and white performances on psychometric mental ability tests, while the second chapter provides a review of the research into race and sex differences in brain size and cognitive ability. Other topics covered include: the relationship between the g factor and infant intelligence; the cognitive correlates of intelligence and personality; an historical overview of the founders of the scientific study of intelligence, Binet and Galton; and a review of the mental speed approach. The volume concludes with a discussion of the effects of intervention programmes on accelerating the development of intelligence within the context of Piaget's criteria for the assessment of durable training methods.