NEW YORK AND LONDON
D. APPLETON AND COMPANY
1915

Copyright, 1915, by

D. APPLETON AND COMPANY

Printed in the United States of America

TO MY COLLABORATORS IN THESE RESEARCHES

DANIEL DE LA PAZ
ALFRED T. SHOHL
WADE S. WRIGHT
ARTHUR L. WASHBURN
HENRY LYMAN
LEONARD B. NICE
CHARLES M. GRUBER
HOWARD OSGOOD
HORACE GRAY
WALTER L. MENDENHALL

WITH PLEASANT MEMORIES OF OUR WORK TOGETHER

PREFACE

Fear, rage and pain, and the pangs of hunger are all primitive experiences which human beings share with the lower animals. These experiences are properly classed as among the most powerful that determine the action of men and beasts. A knowledge of the conditions which attend these experiences, therefore, is of general and fundamental importance in the interpretation of behavior.