ence.

Should the book appear unduly long in prospect, the longest and most
detailed chapter, that on Sensation, might perfectly well be omitted,
on the first reading, without appreciably disturbing the continuity of
the rest.

On the other hand should any reader desire to make this text the basis
of a more extensive course of reading, the lists of references
appended to the several chapters will prove of service. The books and
articles there cited will be found interesting and not too technical
in style.

Much advantage can be derived from the use of the "Exercises". The
text, at the best, but provides raw material. Each student's finished
product must be of his own making. The exercises afford opportunity
for the student to work over the material and make it his own.

A first or preliminary edition of this book, in mimeographed sheets,
was in use for two years in introductory classes conducted by the
author and his colleagues, and was subjected to exceedingly helpful
criticism from both teachers and students. The revision of that
earlier edition into the present form has been very much of a
cooeperative enterprise, and so many have cooeperated that room could
scarcely be found for all their names. Professor A. T. Poffenberger,
Dr. Clara F. Chassell, Dr. Georgina I. Gates, Mr. Gardner Murphy, Mr.
Harold E. Jones and Mr. Paul S. Achilles have given me the advantage
of their class-room experience with the mimeographed book. Dr.
Christine Ladd-Franklin has very carefully gone over with me the
passages dealing with color vision and with reasoning. Miss Elizabeth
T. Sullivan, Miss Anna B. Copeland, Miss Helen Harper and Dr. A. H.
Martin have been of great assistance in the final stages of the work.
Important suggestions have come also from several other universities,
where the mimeographed book was inspected.

R. S. W.
Columbia University
August, 1921

CONTENTS

CHAPTER I

PAGE

WHAT PSYCHOLOGY IS AND DOES 1

Varieties of Psychology 2

Psychology as Related to Other Sciences 5

The Science of Consciousness 7

The Science of Behavior 8

Introspection 10

Objective Observation 11

General Lines of
Psychological Investigation 14

Summary and Attempt at a Definition 17

Exercises 19

References