ANIMAL INTELLIGENCE [Illustration] THE MACMILLAN COMPANY NEW YORK · BOSTON · CHICAGO SAN FRANCISCO MACMILLAN & CO., LIMITED LONDON · BOMBAY · CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, LTD. TORONTO ANIMAL INTELLIGENCE EXPERIMENTAL STUDIES BY EDWARD L. THORNDIKE TEACHERS COLLEGE, COLUMBIA UNIVERSITY New York THE MACMILLAN COMPANY 1911 _All rights reserved_ COPYRIGHT, 1911, BY THE MACMILLAN COMPANY. Set up and electrotyped. Published June, 1911. Norwood Press J. S. Cushing Co.—Berwick & Smith Co. Norwood, Mass., U.S.A. PREFACE The main purpose of this volume is to make accessible to students of psychology and biology the author’s experimental studies of animal intellect and behavior.[1] These studies have, I am informed by teachers of comparative psychology, a twofold interest. Since they represent the first deliberate and extended application of the experimental method in animal psychology, they are a useful introduction to the later literature of that subject. They mark the change from books of general argumentation on the basis of common experience interpreted in terms of the faculty psychology, to monographs reporting detailed and often highly technical experiments interpreted in terms of original and acquired connections between situation and response. Since they represent the point of view and the method of present animal psychology, but in the case of very general and simple problems, they are useful also as readings for students who need a general acquaintance with some sample of experimental work in this field. It has seemed best to leave the texts unaltered except for the correction of typographical errors, renumbering of tables and figures, and redrawing the latter. In a few places, where the original text has been found likely to be misunderstood, brief notes have been added. It is hard to resist the impulse to temper the style, especially of the ‘Animal Intelligence,’ with a certain sobriety and restraint. What one writes at the age of twenty-three is likely to irritate oneself a dozen years later, as it doubtless irritated others at the time. The charitable reader may allay his irritation by the thought that a degree of exuberance, even of arrogance, is proper to youth.