are really significant; and second, as to the methods of observation which are likely to yield results which are worth while.
During R.'s first twenty months he was an only child in a small family of adults. The advantages of having as the subject for one's observations an only child are obvious enough. The disadvantage is that a child thus isolated from his kind probably falls short of being a typical child. Still, this disadvantage tells more strongly in later childhood than in infancy and early childhood.
In the preparation of the Studies, I have received much assistance from Preyer's pioneer work, "The Mind of the Child" (English translation, in two volumes, by Professor H. W. Brown); Professor Sully's "Studies of Childhood"; Miss Shinn's "Notes on the Development of a Child," and her delightful volume, "The Biography of a Baby"; and Professor Baldwin's "Mental Development in the Child and the Race." I have also consulted a large number of books and articles on special points, and acknowledgment of the help received from them is made in footnotes and references throughout the work.
It is a pleasure to acknowledge the invaluable service rendered by my colleague, Dr. A. E. Davies, in revising the work in manuscript. I have further to thank Professors E. B. Titchener and G. M. Whipple of Cornell University, who read critically the greater part of the book in manuscript, for many valuable sugges-
