The debate on intelligence has been polarized between those who see it as a biological property, genetically determined, and those who see it as the property of knowledge systems, culturally determined. Anderson proposes a theory based on a synthesis of these two positions. He argues that while knowledge itself is a extrinsic cultural phenomenon, the mechanisms by which it is processed are innate components of individual brains. The rate and efficiency of knowledge acquistion is crucially determined by these mechanisms which vary from individual to individual according to genetically-determined biological factors. However, he argues that the development of intelligence can also be determined by the acquisition of new competences which are not genetically determined. Finally, the book analyzes such topics as infant intelligence, mental retardation and cognitive development in the light of this theory.