Originally published in 1942, this title attempted to trace, from their very earliest appearances after birth, all aspects of mental development in childhood up to the age of about 4 or 5. It is based largely on the author's almost daily observations of his own five children, over a period of some twenty years, supplemented by numerous tests and experiments.

The first purpose of this book was to advance our knowledge of the psychology of childhood. The importance of such knowledge had become increasingly recognised. Even if not all is completely determined in the first 4-5 years, there was little doubt by this time that these first years are of profound significance for future development: and the better understanding and training of the young child may be at the root of many of our educational and social problems.