First published in English in 1969, the book opens with a chapter by Pierre Oleron on intellectual activities. These fall into three groups: inductive activities (the apprehension of laws, relations and concepts), reasoning and problem solving. It describes typical methods and essential results obtained by relevant experiments. There are two chapters by Jean Piaget and his collaborator Barbel Inhelder. The first, on mental images, breaks new ground: it describes original experiments carried out by Piaget and associates with children of various ages. Piaget examines the relations between...