PREFACE V

cepted classifications and terms, to introduce those experiments which hâve coine into most gênerai favor, and to leave untouched those fields in which experiment has been of doubtful value. The discussion on each topic is limited to the bearings of the experiment.

As to the method of using the book, each instructor will naturally adopt that best suited to his situation. If space is available, the students should be encouraged to perform the experiments in the rooms of the department during certain open hours, and under the gênerai supervision of an assistant. There should be sufEcient time allowed in the recitation-period for spécial suggestions and directions to the students, and for reports upon the completed experiment. The students' notes on each topic must be coUected and checked rigorously ; for, no matter how explicit the directions may be, the quality of the work must be passed upon by the instructor. It is profitable to require the students to take turns in working over the reports to show difficulties, original observations, spécial démonstrations, etc. Ordinarily each experiment will take two hours. The first experiment should be divided into two assignments, on account of the newness of the work aud in order to avoid fatigue.

Titchener's monumental four-volume set of laboratory manuals is a most valuable compendium.* It contains bibliographies, besides technical discussions of nearly every topic in this course. Sanford's,t Wit-

*Titchener, "Expérimental Psyehology": Qualitative (I) Student's Manual and (II) Instructor's Manual; Quantitative (III) Student's Manual and (IV) Instructor's Manual.

t Sanford, "Expérimental Psychology."

vî PKEFACE

mer' s,* and Judd'st manuals are helpful références. Baldwin's dietionary of Philosophy and Psychology should also be on the reference-table, together with the most approved elementary texts.

The author has gleaned material from many sources and wishes hère to acknowledge his grateful obligations to those who find themselves contributors to this volume. He has had the benefit of helpful advice from many psychologists of expérience ; several of them hâve kindly read the manuscript and made valuable suggestions. He is especially indebted to his coUeague Dr. Mabel Clare Williams for coopération.

*Witmer, "Analytical Psychology."

f Judd, "Laboratory Manual of Psychology^* and "Laboratory Equipaient for Psychological Experiments."