From the preface: “Rapid progress in the psychological study of problems in education has taken place since this book was first written in 1922. Many new fields have been explored and many theories, in good repute in 1922, have lost prestige as the result of scientific investigations. In this revision much new material is therefore included and many familiar theories have been discarded or revised………….New discoveries in educational psychology and additional information concerning the needs of students have led to changes so extensive as to require rewriting of the entire book.“