Originally published in 1931, the study reported in this book was undertaken as part of the research programme of the Canadian National Committee for Mental Hygiene. It represents a systematic inquiry into the social and emotional behaviour of pre-school children as observed from day to day in a nursery school. The study extended over a period of three years, and it concerned children between the ages of two and five years who were in attendance at the McGill University Nursery School and child laboratory. It can now be read and enjoyed in its historical context.