The Mental Life of Monkeys and Apes A Study of Ideational Behavior   By: Robert M. Yerkes (1876-1956)

ROBERT M. YERKES Harvard University

BEHAVIOR MONOGRAPHS Volume 3, Number 1, 1916 Serial Number 12 Edited by JOHN B. WATSON The Johns Hopkins University

WITH SIX PLATES AND FIVE TEXT FIGURES

CONTENTS

I. Interests, opportunity and materials

II. Observational problems and methods

III. Results of multiple choice experiments:

1. Skirrl, Pithecus irus 2. Sobke, Pithecus rhesus 3. Julius, Pongo pygmaeus

IV. Results of supplementary tests of ideational behavior:

1. Julius, Pongo pygmaeus : Box stacking experiment Box and pole experiment Draw in experiment Lock and key test 2. Skirrl, Pithecus irus : Box stacking experiment Box and pole experiment Draw in experiment Hammer and nail test Other activities 3. Sobke, Pithecus rhesus : Box stacking experiment Draw in experiment Box and pole experiment Other activities

V. Miscellaneous observations:

1. Right and left handedness 2. Instinct and emotion: Maternal instinct Fear Sympathy

VI. Historical and critical discussion of ideational behavior in monkeys and apes:

1. Evidences of ideation in monkeys 2. Evidences of ideation in apes

VII. Provision for the study of the primates and especially the monkeys and anthropoid apes

VIII. Bibliography

I

INTERESTS, OPPORTUNITY AND MATERIALS

Two strong interests come to expression in this report: the one in the study of the adaptive or ideational behavior of the monkeys and the apes; and the other in adequate and permanent provision for the thorough study of all aspects of the lives of these animals. The values of these interests and of the tasks which they have led me to undertake are so widely recognized by biologists that I need not pause to justify or define them. I shall, instead, attempt to make a contribution of fact on the score of each interest.

While recognizing that the task of prospecting for an anthropoid or primate station may in its outcome prove incomparably more important for the biological and sociological sciences and for human welfare than my experimental study of ideational behavior, I give the latter first place in this report, reserving for the concluding section an account of the situation regarding our knowledge of the monkeys, apes, and other primates, and a description of a plan and program for the thorough going and long continued study of these organisms in a permanent station or research institute.

In 1915, a long desired opportunity came to me to devote myself undividedly to tasks which I have designated above as "prospecting" for an anthropoid station and experimenting with monkeys and apes. First of all, the interruption of my academic duties by sabbatical leave gave me free time. But in addition to this freedom for research, I needed animals and equipment. These, too, happily, were most satisfactorily provided, as I shall now describe.