The Mind of the Child, Part II: The Development of the Intellect, International Education: Series Edited by William T. Harris, Volume IX.

This is one of the first rigorous scientific studies of how children think, written when the study of the developing mind was barely a field at all. William T. Preyer observed his own daughter with the precision of a naturalist, tracking when she began to form memories, solve problems, and engage in logical thought long before she had words for any of it. The radical argument at the book's core: thinking does not require language. Babies reason, remember, and construct mental models of the world using whatever cognitive tools they possess, long before they can name what they know. Preyer meticulously documents stages of intellectual growth that sound surprisingly modern: the emergence of object permanence, the ability to compare and categorize, the gradual construction of causal understanding. He draws on sensory experience as the foundation for all cognitive development, arguing that the child builds the mind from raw percepts gathered through sight, sound, touch, and movement. The book stands as a remarkable artifact of empirical psychology in its infancy, a father-scientist sitting at the cradle with a notebook, determined to understand what actually happens inside a growing brain. For readers interested in the history of psychology, the foundations of child development research, or the eternal question of how we come to know what we know, this volume remains a fascinating window into the origins of the field.