PREFACE The general purpose with which this book has been written is sufficiently indicated by its title. I have selected a number of the ‘ classical ’ experiments of Experimental Psychology, and have tried to present them in such a way that their perform¬ ance shall have a real disciplinary value for the undergraduate student. Within this general purpose, my aim has been two¬ fold. I have sought to show, in the first place, that psychol¬ ogy is above the laboratory : that we employ our instruments of precision not for their own sake, but solely because they help us to a refined and more accurate introspection. And secondly, just as in my Outline of Psychology and Primer of Psychology I gave the results of experimentation a prominent place in the psychological system, so here I have treated the selected experiments not as separate exercises, but as points of departure for systematic discussion. I hope that the book may find its sphere of usefulness. I sorely felt the need of some such guide when I entered the Leipzig laboratory, and I have felt it as sorely throughout my teaching experience. It is needless to add that, although eight years have gone to its making, the Manual falls lamentably short of its ideal. A book in conception is a perfect piece of workmanship : the book that leaves the author’s hands is but a rough approximation to the first design. My greatest debt, here as elsewhere, is to Wundt. I was impelled towards experimental psychology by dissatisfaction with the logical constructions of the English school ; and it was Wundt who taught me the essential lesson of systematic introspection. If my recent writing has seemed rather to be directed against Wundtian doctrines, that is but the natural vii