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The Mental Life of Monkeys and Apes:
A Study of Ideational Behavior
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