"A wonderful, readable summary of what we know about intelligence." Dylan Wiliam, Institute of Education The scientific evidence is clear: IQ tests are extraordinarily useful. IQ scores are related to a huge variety of important life outcomes like educational success, income, and even life expectancy, and biological studies have shown they are genetically influenced and linked to measures of the brain. Studies of intelligence and IQ are regularly published in the world's top scientific journals. This book is an entertaining introduction to the state of the art in intelligence and IQ, and shows how we have arrived at what we know from a century's research. It engages head-on with many of the criticisms of IQ testing by describing the latest high-quality scientific research, and makes a positive case for IQ research, focusing on the potential benefits for society that a better understanding of intelligence can bring.