Psychological research into human intelligence and abilities presents us with a number of difficult questions: critically evaluates research evidence from the past 100 years to consider these and other issues. It shows that, despite the apparent contradictions in this research, the evidence in fact supports one coherent model, a fact which has clear implications for researchers, educators and test-users. This clear and engaging text provides an up-to-date evaluation of what the empirical evidence tells us about the number, nature and origins of human abilities. It will be essential reading for students and practitioners of psychology and education, and also for users of ability tests such as applied psychologists and personnel managers.