The Mentality of Apes

Wolfgang Köhler demonstrated that chimpanzees could solve ­problems by applying insight. His research showed that the intellectual gap between humans and chimpanzees was much narrower than previously thought. The work was revolutionary when originally published in 1917 in German, but it was largely ignored for decades because it violated the conventional wisdom that animal behavior is simply the result of instinct or conditioning. However, Köhler’s research showed this was not the case. He used four chimps in his experiments, Chica, Grande, Konsul, and Sultan. The experiments consisted of placing chimpanzees in an enclosed area and presenting them with a desired object that was out of reach. In one experiment, Köhler placed bananas outside Sultan’s cage and two bamboo sticks inside his cage which needed to be put together to reach the bananas. Köhler demonstrated the solution to Sultan by putting his fingers into the end of one of the sticks. After some contemplation, Sultan put the two sticks together and was able to reach the bananas. As Jaan Valsiner shows in his introduction to this classic work, Köhler’s analysis of the intelligence of apes marked a turning point in the psychology of thinking and the continuing struggle between ­behaviorism and cognitive psychology. Köhler achieved his two-fold aim: to ­determine the relationship between the intellectual capacity of higher primates and man, and to gain insight into the nature of intelligent acts.

Wolfgang Köhler (1887–1967) was a German psychologist and a major contributor to the creation of Gestalt psychology.

Jaan Valsiner is Niels Bohr Professor of Cultural Psychology at Aalborg University, Denmark.

The Mentality of Apes

Wolfgang Köhler Translated from the second revised edition by Ella Winter First Published in paperback, with an introduction by Jaan Valsiner 2019 by Routledge 52 Vanderbilt Avenue, New York, NY 10017 and by Routledge 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN First Published in 1925 Second Edition (revised and reset) 1927 Reprinted 1948, 1973 First Published in a Liveright Paperback edition 1976 by arrangement with Routledge and Kegan Paul Ltd. Reprinted, 2013 Routledge is an imprint of the Taylor & Francis Group, an informa business © 2013, 2019 Taylor & Francis The right of Wolfgang Köhler to be identified as author of this work has been asserted by him in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data A catalog record has been requested for this book ISBN: 978-0-415-20979-3 (hbk) ISBN: 978-1-4128-6540-1 (pbk) ISBN: 978-1-351-29496-6 (ebk) Typeset in Times NRMT Pro by Servis Filmsetting Ltd, Stockport, Cheshire Contents

Preface vi The place of innovation in the lives of apes: Wolfgang Köhler in his context viii Jaan Valsiner

Introduction 1 1 Roundabout methods 11 2 The use of implements 26 3 The use of implements (cont.) Handling of objects 69 4 The making of implements 101 5 The making of implements (cont.) Building. 136 6 Detours with intermediate objectives 176 7 “Chance” and “imitation” 189 8 The handling of forms 231 Conclusion 270

Appendix: some contributions to the psychology of chimpanzees 275 Index 336 Preface

This book contains the results of my studies in the intel- ligence of Apes at the Anthropoid Station in Tenerife from the years 1913–1917. The original, which appeared in 1917, has been out of print for some time. I have taken this opportunity of making a few changes in the critical and explanatory sections, and have added as an Appendix some general considerations on the Psychology of Chimpanzees. With various recent books and essays on the subject I shall have an opportunity of dealing in a further contri- bution to the subject not yet completed. W. Köhler Berlin, October 1924.

Translator’s note The terminology used in this translation was agreed upon after detailed discussion between author and translator. Often the only method possible of covering all the impli- cations of the German terminology was to use several dif- ferent English terms: as has been done with such words as Einsicht, Umweg, Gestalt, das Zueinander von Gestalten, etc. Attention has been drawn to most of these cases in translator’s footnotes. Preface vii

The paragraphs in square brackets, correspond to sec- tions printed in small type in the original, and denote supplementary explanations or digressions. Ella Winter. The place of innovation in the lives of apes

Wolfgang Köhler in his context

Jaan Valsiner

This classic book in psychology is remarkable in its simplicity. It is a description of the lives of a group of chimpanzees and investigators brought together in the world’s first research center to study primates. Established just prior to the turmoils of World War I, both the researchers and researches became stranded on the beautiful island of Tenerife for the duration of the whole war. Its author—then a young man in his mid- twenties—was considered by his mentor Carl Stumpf to give promise for further advancement of psychology as science. Stumpf was right—Wolfgang Köhler became one of the leading figures in the 20th century psychology. But at the time the young man had been enamoured by the ways physicists at the time conducted their science. He had no previous knowledge of experience with chim- panzees. Neither had the chimpanzees of him, or of other strange humans who acted as researchers. The encounter of the two species during the years on Tenerife were a mid-way house in the life courses of both. The author was promoted to the directorship of Germany’s leading psychology institute in Berlin, and the animals entered into their roles as ambassadors of their species for the visitors to the Berlin Zoo. The place of innovation in the lives of apes ix

Wolfgang Köhler may have had no prior experience with apes when he arrived at Tenerife, but he certainly was curious about the ways in which the mind worked. It was a pioneering work to start to understand the men- tality of apes. What he accomplished in the world’s first primate research laboratory was seminal. There was a need to establish a timely experiential “window of oppor- tunity” to observe the general principles of the minds of other species. That could not be done in zoos—where animals were on display for human interests, and where they are kept in far from natural circumstances. This also could not be done in human “home conditions”—in cases where inquisitive human researchers raised young chim- panzees alongside their own children (see Mironenko, 2010). These courageous experiments in human upbring- ing brought in interesting evidence on the limits of adapt- ability to human conditions—but left science blind about their adaptation in nature. The Tenerife experience was a meeting ground of two life-worlds: that of humans (represented by the mind of Köhler and all of his conspecifics thinking of relations with animals), and that of the primates (represented by the 7 (later 9) chimpanzees, and one orangutan, in the Center). Occasionally other experimental subjects— chicken and children (Köhler’s own) become participants in his studies on Tenerife. Köhler was systematic and productive—in a short period of time managing to carry out a research program that has remained crucial for the very foundations of psychological science ever since. The present book is the main result of his work. It is overwhelmingly descrip- tive—telling us the stories about how chimpanzees tried, and succeeded, in solving problems that were inserted into their everyday life realities. The researchers played tricks on the animals—by putting the important resources x The Mentality of Apes

(bananas) in places out of reach, but with potential materials around to make getting to them in principle possible. Descriptions of how they succeeded leave the reader with the feeling of awe and appreciation of the intellectual potential of our closest animal relatives. The “Aha-effect” is not there only in the animals who reach a breakthrough in finding a solution to the given puzzles, but also will surface in the human readers. For them, The Mentality of Apes is filled with instances of creative innovations that the large hairy creatures produced for the watchful eye of the young German scholar. What the reader of this book encounters is the basic question of mentality of survival. In case of chimpanzees this was simple—how to get food. For researchers it was complex—what does chimpanzee behavior tell humans about their own intelligence, and of their own roots? The observations made a century ago remain vivid in the skill- ful presentation of the details that the present book is filled with; we learn about the most incredible inventions by the chimpanzees in their “open air” semi-naturalistic laboratory. More importantly for science, the theoretical implications from the careful observations Köhler made in his experimental settings on Tenerife remain actual in primate research today—even as the focus on that research now is of different general focus than that on Tenerife a century ago.

Wolfgang Köhler: a humanistic physicist in psychology Wolfgang Felix Ulrich Köhler was born in Tallinn, Estonia (then Reval) on January 9, 1887. His father, Franz Köhler, was the director of the Reval Domschule— located on the top mountain part of the ancient city of Tallinn, a few hundred meters from the Domkirche. The place of innovation in the lives of apes xi

Coming out of the Baltic German roots made the family both fortunate (by their social position in the Baltic soci- ety) and unfortunate (vulnerable to the language policies of the Russian Empire in the 1880s–90s). The German language—for centuries safely in place in the Baltic German social world (Plath, 2011) was suddenly made unavailable as a teaching language in the Baltic areas. This—as well as the parents’ desire to give better educa- tion for their children—was the reason why the whole Köhler family left Estonia when Wolfgang was six years old (Allik, 2006). The move to Germany was indeed productive for the children’s education. There Wolfgang Köhler entered his university studies—1905 in Tübingen, 1906 in Bonn, and 1907–1909 in Berlin. It was usual at that time of freedom from numerus clausus for German students to move freely between universities in the search for the best possible education. Köhler certainly had the best education avail- able in Germany at the time.

The attractions of Berlin Köhler’s final university education took place in Berlin. The university in Berlin provided the best for the young man who divided his focus between physics (under the teaching by Max Planck) and psychology (Carl Stumpf). The latter was a central figure in German psychology at the turn of the 20th century who propagated linkages with other disciplines (medicine, education—Stumpf, 1930). Stumpf had long-term intellectual connections with the philosophy of Franz Brentano. In Berlin Stumpf established the Psychological Seminary in 1894 (Institute from 1900 onwards) that was in direct competition with Wilhelm Wundt’s well-known laboratory in Leipzig (open since 1879). xii The Mentality of Apes

Stumpf was really the person behind Köhler’s promo- tion as an up and coming leader in German psychol- ogy. Yet he was not the first candidate for the job once it became determined that the primate center would be established. The first and perfectly fitting candidate was Oskar Pfungst (Garcioa and Gonzalez, 2005, p. 43)—the clever researcher who had revealed the mystery behind the mysterious arithmetic calculation capabilities of a horse (“clever Hans”). When the directorship issue came up in 1912, Pfungst was 38 years of age, and very well prepared for studies of various animal species. Yet he did not want the job. This left the position open for younger candidates—all of whom were in their 20s, eager, but inexperienced. Stumpf proposed Köhler in 1913, but was not successful. A year later he succeeded and Köhler was appointed to the position of Director of the Tenerife sta- tion, where he worked from 1914 onwards. Stumpf appre- ciated his work and understood its profound relevance.1 His promotion of Köhler continued over his lifetime. After Köhler’s return from Tenerife in 1920 he arranged the institutional personnel decision in ways that made it possible for Köhler to take over his leadership role in the Institute in Berlin. By that institutional move the future of the Berlin Gestalt School was guaranteed after Stumpf’s retirement. It is important for leading figures in a science to have a chance to set up working conditions for one’s follower. Stumpf had the wisdom to appoint a young and promising scholar who would develop further his ideas but in a new way. Köhler and other Berlin Gestaltists (Wertheimer, Lewin, Duncker) did not disappoint him. Köhler, on his side, was deeply grateful to Stumpf for his support—his first theoretical book (Köhler, 1920) was dedicated to Stumpf. Köhler’s intellectual credo in psychology was that of a physicist. He would devise psychology experiments with a The place of innovation in the lives of apes xiii careful theoretical mindset like a physicist would do—for each theoretical issue there is a new method constructed. For example—the study of “intelligence” by the time of Köhler’s beginning to work on Intelligenzprüfungen of apes had already moved into the use of standardized methods—intelligence tests. In no place in Köhler’s work would one find any effort to develop such a “test” to “measure” the “intelligence of apes” in general. Instead, we are carefully guided through a step-by-step more com- plex series of tasks for which the action would show the actual structure of intellectual capacities of the animal. Max Planck’s importance in Köhler’s psychological con- tributions is obvious in the latter’s writings (Köhler, 1920) as well as in his insistence that physics be the model for psychology as science. Subjectivity was not to be included in that science—even if it was recognized as a relevant starting point for people’s perception of the world. The contrast that has deeply divided psychology since 1879—between self-perception (Selbstwahrnehmung)— target for scientific investigation—and self-observation (Selbstbeobachtung)—was for the young Gestalists tilted towards the former. After finishing his Doctor of Philosophy degree in Berlin in 1909, Köhler moved to Frankfurt-am-Main to become a Privatdozent at Friedrich Schumann’s Psychological Institute at the local vocational school (which became Johann Wolfgang Goethe University of Frankfurt am Main in 1914—Abides, 1915). He married young artist Thekla Achenback, who started her repro- ductive career shortly that led to her giving birth to four children from Köhler, and divorcing him sixteen years later. He also met there young intellectually eager and intelligent men. Max Wertheimer (1880–1943) arrived there at age 30, Kurt Koffka (1886–1941) came at 24. The year they overlapped in Frankfurt (1910–11) was crucial xiv The Mentality of Apes for the establishment of the Gestalt Psychology tradition that later (since 1922) became institutionally fortified in Berlin, until the Nazi takeover. Köhler, with his fasci- nation for physics (later evident in Köhler, 1920), fitted well with Wertheimer’s similar mode of thinking. The basic ethos of the ideas for experiments with chimpanzees in Tenerife in 1914–16 was fully in resonance with that of Wertheimer’s whose only research participants were human beings. Köhler’s own thinking prior to the work on Tenerife was dedicated to the primacy of perceptual phenomena and resisting explanations of “psychologis- tic” kind that were the target for disputes among psy- chologists (Köhler, 1913).

The journey to Tenerife: the world’s first primate research station Prior to accepting to be the Director of the Tenerife Primate Station in 1914 for a year,2 Köhler had been at the Frankfurt Psychological Institute for three years, collaborating with Max Wertheimer and Kurt Koffka in reaching a theoretical solution to the question of how the human mind functions. Their solution—later to be developed into the theoretical credo of the Berlin School of Gestalt Psychology—was built on the specific focus on how the structured situation of organism related to the environment, frames thinking processes. The roots of this theoretical stance were in physics. The ques- tions that Köhler asked from the chimpanzees through ­experiments were phrased in terms of the discussions of the issues of the wholes in psychology since the 1890s,3 and by his learning with Max Planck in his Berlin study years. The chimpanzees were also not naïve. They came to Tenerife, or more appropriately were taken to it as The place of innovation in the lives of apes xv captives, from Cameroon and Nigeria. Their lives were used first to life conditions in the wild, and then in cap- tivity. In our present-day terms the animals with whom Köhler started his studies were for almost a year previ- ously rehabilitated in the newly established Station from the impacts of having been held captive (Rothmann and Teuber, 1915).4 The role of another young psychol- ogy graduate—Eugen Teuber (1890–1958)—as the first Director of the Primate Station (in the year 1913)—was pivotal in this rehabilitation process. Having studied Völkerpsychologie in Leipzig with Wilhelm Wundt ear- lier, Teuber introduced what in our times could be con- sidered “person-oriented approach” to the chimpanzees in providing them with personal support when needed. The animals seem to have remembered that seven years later when he and his son Hans-Lukas5 visited them in Berlin Zoo (Teuber, 1994, p. 574). Aside from the pioneering status—the Tenerife research station was the first such research center in the world dedicated to the study of apes in quasi-free ­environments—it was built on the assumptions of the value of interdisciplinary scholarship that continues to develop in our times, a century later. It was a collabo- ration between medical sciences and psychology. The mastermind behind the plan was Berlin medical scientist Max Rothmann (1868–1915), in collaboration with psy- chologist Carl Stumpf. Stumpf—as the Director of the Psychological Institute of Berlin University until 1922 (when Wolfgang Köhler took over the post)—was not only an intellectual link for psychology in Germany with the Franz Brentano tradition in Austria, but also a strong supporter of expanding psychology toward ethnology. His collection of folk music from all over the world was a pioneering data source for ethnomusicology. Köhler had finished his doctoral dissertation under Stumpf ’s xvi The Mentality of Apes guidance in 1909, followed by Habilitatsionschrift with Friedrich Schumann in Frankfurt in 1911 (Gerhardt et al., 1999, p. 260). He was ready for an academic posi- tion, but there were very few for such young persons. Stumpf saw the promise in the young man. Already in 1913 he was actively promoting Köhler’s candidacy for the Director of the Tenerife station. He did not succeed at first—Rothmann appointed Eugen Teuber into that role for the first year (1913). Köhler succeeded him for 1914, and, as the history developed its own ways—stayed there until the end (1920). The main waves of studies were conducted by him in the first half of 1914, followed by the second wave in 1916. Financial support, as well as the institutional fram- ing for the primate research center came from three pri- vate foundations together with the Prussian Academy of Sciences. For the latter, entering into primate studies would have—aside from the scientific agenda—also ideo- logical value for the German state similar to the impact of importing the Pergamon Altar to Berlin in 1879. The encounter of the nine chimpanzees with young German researchers on Tenerife was institutionally to be an affair of the Academy of Sciences, and all of the publications from the studies appeared in its Abhandlungen series until 1920 (Köhler, 1915, 1917, 1918: Rothmann and Teuber, 1915). While the daily activities in living next to the chimpan- zees were mundane, the theoretical issues that were at stake in letting apes find ways to food were highly sophis- ticated. The issue—how intelligent are different species of animals—had been fascinating for psychologists and lay- persons in Europe and the Americas for decades. Note that the question was (and continues to be) phrased in comparative terms, with the presumption that human beings are “more” intelligent than others. In contrast, The place of innovation in the lives of apes xvii the more appropriate question—how are different spe- cies intelligent in their particular life environments—was not asked. Köhler introduced that new question into the field by the ethos of his problem-solving tasks, which were very similar in basic ideas to the ones invented by Max Wertheimer in his only book Productive Thinking (Wertheimer, 1945). Yet he was not asking questions about evolution, and denied the notion of emergence. So did other members of the Berlin Gestalt School—it was the dynamic processes leading to solution (insight6) but not the role of new solutions in the future (foresight) that was Köhler’s interest in the Tenerife years. The chimpanzees were set up in different conditions to their immediate, here-and-now, total living environments that included theoretically relevant opportunities for them. The ways in which the animals tried, and succeeded (or not) to solve these embedded problems were observed and carefully counted. The nomothetic function of idi- ographic observations was the scientific norm at the time—the reader of this book will not find any pres- entation of averaged data, correlation coefficients, and statistics-based arguments in it. Instead, the experiments described—for each individual chimpanzee—are indica- tive of a physicist’s mind.

Back to Berlin, on to America After the work on Tenerife Köhler returned to Berlin in May 1920—never to do any research with primates again. He had, by self-admission, become tired of the fatigue of the constant contact with the apes (Ash, 1997, p. 167). In this he differed from (later) standard dedication of the primate researchers to life in the field. Köhler used the opportunity to work in a new research field trying to solve the old problem—of relation to the Gestalt xviii The Mentality of Apes perspective to that of associationism. But when finished on Tenerife, he was ready to move on. After a short tem- porary professorship in Göttingen (1920–21) he became professor and director of the Berlin Psychology Institute (following the retiring Stumpf). The Berlin Institute, after revolution in Germany in 1918, had relocated to the most fancy place of possible locations—occupying a wing in the former Imperial Palace in the middle of the town in 1920. The high ceilings of the rooms in the palace allowed for unique experiments of controlling the whole visual field of the research participants to be performed (Sprung and Sprung, 1993). The “Berlin tradition” of Gestalt psychology from 1911 to the 1930s re-focused the empirical realm of studies within that framework from acoustic (Stumpf’s legacy) to behavioral (Köhler’s stud- ies in Tenerife) to visual perception and reasoning (Max Wertheimer, Karl Duncker). Köhler played a pivotal role in the international proliferation of the ideas of the Berlin Gestalt tradition—as a visiting professor at Clark University (1924–25) and Harvard and Chicago (1934 and 1935). He also visited Brazil and Argentina in 1932. Köhler’s work continued in the United States after leaving Germany in 1935. He publicly objected to the Nazi regime policies of dealing with university employees on ethnic grounds. Very few academics in Germany had the courage to publicly criticize the regime, and Köhler expected repercussions—which failed to come. In 1935 he received a professorship from Swarthmore College in Pennsylvania where he stayed until his retirement in 1956. Afterwards, until his death (June, 11, 1967), he lived on his farm in Enfield, New Hampshire, and was research professor in nearby Dartmouth College. Although his theoretical ideas did not find further development in the New World, his personable humanistic ways of being made him fit well into the community of psychologists The place of innovation in the lives of apes xix in North America. In a conceptual obituary to his work, Solomon Asch remarked:

As a mind that ranged subtly over different prov- inces of knowledge, Köhler was a notable figure in the intellectual history of this century. He was also a great teacher in psychology. He was one of the major efforts to bring order into the discipline. It was a fruitful effort: he made new, important additions to psychological knowledge and thought; he opened new fields of inquiry, systematized known facts, and shed light on problems that await investigation. He combined in one person many of the diverse faces of scientific activity. There was a faithful observer who described natural events with unsurpassed clarity and evident enjoyment, whether these were the actions of a chimpanzee or the appearance of a visual scene. He was also the discoverer of unsuspected phenomena, the bold theorist who discovered similarities between hitherto disparate regions of events, and the trench- ant experimenter. Underlying all these was his cease- less effort to comprehend the place of psychological events in nature. (Asch, 1968, pp. 118–119)

I think Köhler’s ways of phenomenological experimenta- tion are particularly important to understand when one reads The Mentality of Apes. Seemingly it is a colorful empirical account of what happened as the apes were confronted by tasks that required using a detour, or an implement, or even constructing one. Yet the key to the successes of the apes was the careful strategic move of the experimenter who created challenges so as to see if the animals could proceed yet one step further. These moves were made on the basis of a background theoreti- cal system—that of Gestalt psychology in the form of field xx The Mentality of Apes theory—that was in the making in Köhler’s mind and elaborated on during his Tenerife years (Köhler, 1920). As a good physicist Köhler, like Einstein (Hentschel, 1992), was never an “empirical scientist” as 21st century psychol- ogists would value. He was a true scientist who carefully studied empirical evidence that was crucial for proving theoretical points—not for the sake of accumulating data. The role of the data became crucial in specific ways, as the role of science is arrival at generalized knowledge.

General major contributions Köhler was (with Kurt Koffka and Max Wertheimer) the originator of what is by now known as the “Berlin tradition” of Gestalt psychology, which started in the Frankfurt years of the three. The undisputed master- mind of the theoretical side of the tradition was Max Wertheimer, yet Köhler’s publication after the return from Tenerife (the present book—Köhler, 1921—as well as others (Köhler, 1920, 1922a, 1922b, 1929, 1935, 1940, 1969) emerged as the primary sources on this tradition. Continuing with the tradition of rivalry between Berlin and Leipzig orientations from the times of Carl Stumpf and Wilhelm Wundt, the Berlin tradition rejected the subjectivity-oriented Ganzheitspsychologie of the Second Leipzig School of Felix Krueger and Hans Volkelt (Diriwächter, 2013) which was developing Gestalt- psychological notions from the perspective of develop- mental psychology. Köhler’s perspective was decidedly non-­ developmental—while focusing on the dynamics of the Gestalt. He rejected emergeticist foci in science, similarly to the subjectivist perspectives. The Gestalt principles were laws in themselves—there was no theoretical focus on the “Gestalt maker”.7 The animals he studied—and The place of innovation in the lives of apes xxi on Tenerife these included, aside from the chimpanzees, his own children, dogs, and househen—were shown to operate­ at their species-specific levels differently, to verify the borders between the biological categories. Köhler did not look for evolutionary origins of human cognition in chimpanzee problem solving. Rather he did everything to demonstrate how the mentalities of the species differ, while they still operate by universal Gestalt principles. These general principles led Köhler to look for iso- morphism between the psychological processes and brain activity. Roots of this idea go back to his Tenerife period where he saw clearly the correspondence between the phenomenology of chimpanzee behavior with that of the environmental conditions. This takes the form of a convergence—but not similarity—of the general field- like organization principle of the environment, behavior within it, and—Köhler hypothesized—also in the field- like dynamics of the brain processes. The isomorphism of the fields—with the idea taken from physics to the visual environments (viewed as fields) of the chimpanzees on Tenerife—sets the stage for Gestalts to emerge and be “pregnant” with movement towards an equilibrated field (Köhler, 1920, chapter 2). Isomorphism was to be consid- ered as a principle specifying generalized similarity, not a mirror-image correspondence of the brain processes with their behavioral counterparts (Henle, 1984). In Köhler’s own words,

Experienced order in space is always structurally identical with a functional order in the distribution of underlying brain processes… … experienced order in time is always structurally identical with a functional order in the sequence of correlated brain processes. (Köhler, 1947, p. 39) xxii The Mentality of Apes

The isomorphism principle grows out of physics, sup- ported by the experiments in Tenerife. A potential object loses the interest of chimpanzees as a candidate for tool- making if it becomes part of the structure of the environ- ment. The focus is on the dynamics of field structures, of the environment, and of the perception-action field structure of the animal. Köhler was interested in the role of values in human life and science all his life, but especially after arriving in the United States (Köhler, 1938, 1944).

Special features of the present book Köhler’s axiomatic background was strictly that of a theoretical physicist working in the field of psychol- ogy. Issues of development, emergence, and biological systems were not part of his world view. Dynamics of fields—isomorphically between perception, thinking, and brain dynamics—was his interest in the empirical com- parisons of visual perception and action in chicken, child, and chimpanzees (Köhler, 1915). His was a psychology of the non-humanizing kind. On the one side, his descriptions of the ways chimpanzees acted in Tenerife are given with great respect and feeling into their “animal beings”. He was deeply moved when two of the chimpanzees died. On the other hand—it is strictly the case that no matter the chimpanzees could solve complex puzzles Köhler invented for them, and even as these solutions carry forward over a long time (some testing of achievements of early 1914 was done in the first half of 1916, and successfully), the question of whether they could reach the status of Homo sapiens if they tried hard, was definitely negated. The successes of apes were to tell us the story of Gestalt-reorganization as a general principle. Like Pavlov with dogs, Köhler used The place of innovation in the lives of apes xxiii the chimpanzee evidence to prove general theoretical hypotheses, while the description of the behavior remains given in simple and enjoyable everyday terms. It is also to Köhler’s credit that in the Mentality of Apes there are very few references to the literature of his time. The reader will find them in footnotes—they are few, but they very clearly indicate the substantive links of his theoretically based experimental efforts. This careful use of references is in great contrast to our contemporary practices of fights for recognition through mutual citation networks that often replace reasoning by referencing.

Köhler’s experimental epistemology Köhler developed a strategy of research that fits the qual- itative phenomena in which he was interested. It could be called that of sequential challenging. Once a task gets solved, it is transformed by the experimenter into a modi- fied field structure with new expectations for finding a solution. In this Köhler was a very good example of a sci- entist using the idiographic notion of generalization—yet from a series of singular events produced by a particular animal (i.e. each observation described in the book is given with the name of the animal—no demand for ano- nymity or ill feelings of the chimpanzees). As a result we as readers can develop a general picture of each of his 9 chimpanzees. Sultan’s success in uniting sticks to make an implement reaches the readers as part of the general image of the ape called “Sultan”—not an anonymous code number (e.g. 007). The apes are for us personalized this way, but not humanized. Köhler’s Gestalt-psychological experiment as an event is a form of theater performance in which the direc- tor (Köhler) sets up the stage, and then brings out the actors (chimpanzees) to the stage, with himself and other xxiv The Mentality of Apes personnel assuming the role of the audience. Once one act of the play is over (and the animal either finds a way to solution or abandons the task) the director enters the stage, makes re-arrangements, and lets the actors con- tinue the play. The stage—the courtyard in the Tenerife Station in front of the animal holding places, covered by net above the wire walls of the enclosure—guaranteed that the director was in full control by the external field. Placement of different objects (suggestions for making implements or reaching the goals in a new way) were introduced with careful regard for the animal’s state and location in the field. Hence the animals developed their own version of the field—Umwelt in terms of Jakob von Uexküll (Chang, 2009)—within the constraints the theater director had set up. Furthermore, the theater director prescribed specific roles to the actors. In a number of places in the book we get a glimpse that a chimpanzee observing the actions by peers is outside of the cage, in a position similar to Köhler. Furthermore, Köhler prohibited Sultan (the “more intelligent” chimpanzee—who was still considered “pronounced egoist”—p. 169) at times from intervening with the activities of others when on the scene. At other times he delegated to Sultan the role of demonstrator on how to link two sticks—the “teacher role”. Sultan became a “research assistant” of a kind.8

The findings that were crucial Of course the fame of Sultan—the “stick-maker”— has been the most celebrated of the various findings that Köhler himself highlighted. From the perspective of intellectual capacities the success of putting smaller tubes into a bigger one to make a stick to reach a banana involves coordination of the perceptual, cognitive, and The place of innovation in the lives of apes xxv motor fields. The building of “box towers” had a simi- lar structure—demanding the creation of a whole out of parts to make an implement. The “record holder” Grande managed to create a construction of four boxes (p. 140). Again, like in the case of Sultan assembling a stick, a chimpanzee piling up boxes for climbing to the ceiling where the Director has set up a banana creates one whole—a tower that can support the getting to the banana. The synthetic nature of these tool-making tasks is well demonstrated by Köhler, and it fits his theoretical credo of coordination of the field structures. There were also other findings—well described by Köhler but—as these did not extend the theoretical side of his arguments—remained for him (and for the readers of the book) kind of curious episodes. I would like to ana- lyze three of these from the standpoint of how Köhler’s work links with our contemporary efforts in primatology a hundred years later.

“Pole vaulting”. It becomes revealed in the book (p. 71 ff) that chimpanzees developed functional skills of climb- ing up different non-stationary poles to reach a banana attached to the ceiling. In structural sense their actions constitute a version of pole vaulting that—as human sport—came into being. Human beings have used poles to jump over canals (a “Netherlandic habit”) and already since the 1820s have tried to reach heights by running, placing the pole, and propelling one’s body upwards, until the gravity brings it back from the world record heights of over 6 meters. Chimpanzees, in contrast, would not have such implements around in their regular habitats. The “poles” on which they climb are attached solidly to the ground (trees rooted in ground). The bend- ing “poles”—tree branches—are still solidly attached to the tree trunk, so the experience of trying to climb on a xxvi The Mentality of Apes non-attached pole would be most unlikely in the natu- ral habitats. Neither could this be acquired by imitating humans—neither Köhler nor the animal keepers were practicing pole vaulting at any time in their lives. Nor were they climbing up to any objects holding on to non- stationary poles.9 Köhler created an artefactual need for getting to the bananas attached to the ceiling net. Sultan—after fail- ing to jump high enough to get the banana—“seized a pole that lay in his vicinity, lifted it as though to knock the prize down, and then desisting, put one end of the pole on the ground beneath the objective, and repeated the “climbing jump” (p. 71). The practice of using poles for short time periods (as they stood in a vertical position only briefly) spread from Sultan to three other chimpanzees. Köhler provided one of them (Chica) with a long pole (4 meters—p. 73). The climbing on a non-stationary pole up to the banana, grasping it, and falling down from that height became an established adaptation to the feeding strategies in the station. This idioadaptive10 practice is remarkable because it requires the animal’s understanding of the falling speed of non-attached vertical poles—possibly happening in natural habitats—together with the use of the time moment for climbing. An ape in the forest is unlikely to try to climb up a falling tree, while if such falling object could become integrated into momentary scheme for action (and only such moment used) the use of the temporary verticality—together with anticipatory fall from heights—speaks of a precisely timed high-risk (fall) solution pattern. This is quite different in its total bodily implications from Sultan’s attaching two or three tubes together to make a slowly usable implement. The pole is a stick “assembled” into the action structure in a limited The place of innovation in the lives of apes xxvii moment in time. The coordination of the timing of pole positioning and climbing is crucial for success.

Human beings are potential boxes. Köhler’s innovation of bringing boxes to the stage of the station led to various levels (up to 4) pilings of boxes on top of one another to facilitate climbing to the food. Yet the use of boxes was extended by the chimpanzees beyond the boxes:

Further on in the experiment a curious incident occurs: the animal reverts to older methods, wants to lead the keeper by his hand to the objective, is shaken off, attempts the same thing with me, and is again turned away. The keeper is then told that if Sultan tries to fetch him again, he is apparently to give in, but, as soon as the animal climbs on his shoulders, he is to kneel down very low. Soon this actually happens: Sultan climbs on to the man’s shoulders, after he has dragged him underneath the objective, and the keeper quickly bends down The animal gets off, complaining, takes hold of the keeper by his seat with both hands, and tries with all his might to push him up (p. 143).

Summoning help from the humans, who after all are in control of the whole station, is an ingenious solution to the missing box problem. Obviously the ape has to develop distrust into the solidity of the humans-as-boxes, and face resistance for being assigned a role of an imple- ment. Yet outside of the problem solving task the more general issue—social embeddedness of any study and the inevitable participation of all who are in the situation— becomes emphasized.

What is help? Köhler devoted a special “supplement” (pp. 167–173) to the topic of “building together”. It was xxviii The Mentality of Apes set up as a group activity after all its members had indi- vidually acquired the ways to pile boxes on one another. Köhler was here interested in whether any mutual assis- tance in a similarly functioning group occurs. He failed to find it—instead the juvenile apes were interfering with one another’s plans to get the food from the ceiling. For that purpose, Köhler needed the cooperation of some more skilled others—Sultan in the first place. He claimed to have kept Sultan from helping (p. 168) and then describes Sultan’s transgression:

On one occasion when we had forbidden him to par- ticipate in the building, he could not keep in the role of passive spectator, when Grande had piled up one box on the other, and was still unable to reach the prize. He quickly fetched a third box from a distance of about twelve meters and put it close to the pile: then he squatted down again and watched, although he had not been reminded of my prohibition by either word or gesture (p. 169, added emphasis)

The nuance in the report—the presence of prohibition against helping (from the theater director) and Sultan’s diplomatic solution—bringing usable material to the vicinity of action but not participating in the action itself—allow us to observe the ways in which axioms operate in the research processes. While allowing the researcher to take a close look at the phenomena, they introduce “blind spots” in adjacent areas. The assumption that chimpanzees are qualitatively dif- ferent from humans led to certain rigidity in Köhler’s thought. Certainly this rigidity is based on his premise of the limits of the chimpanzee intelligence—recognizing the cognitive (problem solving) side but refusing to accept The place of innovation in the lives of apes xxix the possibility of the social side of intelligence in the ani- mals. The critically relevant phenomena of such overlook are moments of mutual assistance given by the chim- panzees to one another. Köhler provides astute obser- vational evidence about such momentary help occasions (pp. 167–173), and then spends much space in the book (pp. 168–170) in arguing that the “help” chimpanzees give one another is not comparable to the “real help” (of human beings) who are assumed to give help on altruistic basis (while in chimpanzees “help” is egocentric). This leads him also to pay no attention to the momentary sup- port in the relevant moment to another in the “boxes and pole” task. This is visible in the film version of the record- ings: a chimpanzee has built a tower of two boxes and is trying to set the pole up on top of these so as to climb to get the banana. At an instant another chimpanzee rushes to the scene, holds the pole for a moment (allowing the first one to climb and get the fruit), and rushes off to the side (while the pole + boxes construction crashes and the first chimpanzee who got the fruit falls to the ground). Social assistance at the critical moment of the action sequence without the subsequent sharing of the fruit is hard to explain without assuming a sophisticated form of social understanding by the chimpanzees. Further sophisticated forms of social collaboration were described by Köhler (yet noted to be “without, entirely carrying conviction” that these fully resemble human forms—p. 170 observation of 15th February). Moving over a heavy object to be used as a tool for reach- ing required—and got—joint action to accomplish it. It needed coordination in time and goal orientations. It also required understanding of the value of temporary coop- eration—as was already demonstrated with the “boxes and poles” cooperation. xxx The Mentality of Apes

Primate research today: what has been learned since Tenerife? Köhler was a psychologist interested in the mind and brain relations who by a series of coincidences had the opportunity to study chimpanzees for a relatively short time. Despite the richness of details about the problem- solving efforts by chimpanzees, The Mentality of Apes tells us a story about humans—as for the reader it is their own human experience that makes the book a good read. Köhler had specific theoretical goals that were pur- sued by the fascinating stories about chimpanzee adapta- tion to human-made environments. His focus was not on “primate research”—the study of the whole group of anthropoids—but in the specific cognitive capacities of chimpanzees as triggered by transformation of the field. Science of primatology has developed in a different direction over the course of the 20th century. The arena of specific research on primates—understanding different species in their natural life settings—has developed. The new focus is on primate adaptational possibilities under various conditions in the wild—leading to demonstra- tions of inter-areas variability in the results of such adap- tations. Making and using implements—stones to crack nuts, branches for fishing for termites, leaves to use as sponges—have become commonplace in contemporary primate research. Most possibly Köhler himself would have been sur- prised about the ways in which his observations and experiments on Tenerife fit into our contemporary research directions on the social ecology of higher pri- mates. His experiments demonstrated the flexibilities of the chimpanzees to develop new adaptations to locally varied material conditions. His interpretation of these achievements was in terms of the emerging Gestalt The place of innovation in the lives of apes xxxi theory. As an intuitively astute experimenter, Köhler cre- ated experimental situations that matched the ecological demands of the original ecologies of the chimpanzees. Hence the success of the Tenerife experiments. These findings have been corroborated further by research done on the axiomatic premises directly opposite to those that Köhler espoused (Firsov, 1977, Imanishi, 1984, Matsuzawa, 2001, 2016, Matsuzawa, Tomonaga, and Tanaka, 2006) What from the human point of view seemed a giant leap in cognitive capacities of an ape (e.g. fitting sticks together to “make a tool”)—would be a rather ordinary adaptation to the richness11 of the natural environment. Contemporary primate research has also been a target for economic, political, and ideology that make labo- ratory research on primates disappear—in parallel to the ecological and wartime conditions that are gradu- ally changing the natural habitats. Hence our knowl- edge base about apes becomes constricted—rather than expanded—in the 21st century. This makes careful inves- tigation of the efforts to study primates in the wild, in the “half-way houses” (as on Tenerife), zoos, and human homes (Mironenko, 2010) necessary for any science of cognitive or cultural kind. Summarizing the current state of affairs in the study of higher primates, Cristophe Boesch points out:

Wild animal studies have led to the realization that some of the population differences observed in some species possess close similarities to human cultures. The accumulation of such detailed observations from wild animal populations have provided more and more convincing details about the cultural skills in different animal populations, which has resulted in a shift away from the question, “do animals possess xxxii The Mentality of Apes

culture?” to the question, “what differentiates human cultural abilities from other animals’?” The growing body of evidence of cultural differences, not only in chimpanzees but also in macaques, capuchin mon- keys, orangutans, and other primate species, opens the way to a precise ethnography of culture in differ- ent species (Boesch, 2012, p. 689)

By experimental studies of chimpanzee cognition Köhler set the stage for precisely that future of primate research that his own axiomatic foundations ruled out—the look at the emergence of culture in our closest non-human rel- atives. Chimpanzees invent new forms of adaptation, and maintain these over long periods of time.12 Innovation is the rule of the game—be it in the wild or in a labora- tory of language learning (Segerdahl, Fields, and Savage- Rumbaugh, 2005).

General Conclusion: Why read Mentality of Apes a century later? Köhler’s Tenerife work has reached the state of canoniza- tion in psychology as a “classic”. This status is danger- ous—the positive label may replace the actual ingenuity of the work (and there was much of it—in inventing new experimental probes). Knowing that the given work is a “classic” often stifles the reader from seeing intellectual “holes” in it (e.g., Köhler’s hesitancies about the nature of “help” in chimpanzee social relations), as well as making him or her reluctant to develop the ideas further. The present book is worth reading for the sake of seeing how research works in practice. It reads like an intellectual detective story—only with a positive agenda. Instead of finding out “who killed X” the focus here is “how do we get the banana?” This focus is by far more The place of innovation in the lives of apes xxxiii healthy and enjoyable for any reader who wants to get mental stimulation about how innovation—both for ani- mals and human researchers—can be constantly under consideration. Köhler’s work has been appreciated not because it is a “classic” but because it is a serious account of the ways in which science proceeds. Innovation—not “big data”—is the key.

Acknowledgments The preparation of this work was supported by the Danske Forskningsfond through the Niels Bohr Professorship grant. Constructive suggestions by Jüri Allik of Tartu University in the preparation of this final version are most gratefully acknowledged.

Notes 1 Stumpf’s appreciation of Köhler’s work (around 1923–24) was clear: “Köhler did not attempt biologically useless stunts of calculation; his experiments were concerned with the important life activities of the animals, and he proved that his chimpanzees in their use of tools and detours went far beyond the assumed limits of animal intel- ligence, and showed, in a certain sense, an “intelligent” behavior; only empirically intelligent, of course, not presupposing any general concepts, as arithmetic does” (Stumpf, 1930, p. 407). It was clear in the 1920s that basic science in psychology needs to be qualitative and phenomenological, and that quantification would not reveal anything new about psy- chological functions. This understanding vanished over the six decades onwards from the 1930s (Toomela and Valsiner, 2010) leaving psychology as science hostage to social nor- mativity of methodological fashions of analyses of accumu- lated numbers. xxxiv The Mentality of Apes

2 The original contract Köhler had was for the calendar year of 1914, but the outbreak of World War I necessitated the extension of the contract by the Prussian Academy of Sciences, so that eventually he remained the Director of the Station until it closed down in October 1920, and the remaining chimpanzees were transferred to the Berlin Zoo. 3 The discussions about the notion of the whole (Gestalt, in this book also translated as form) as not reducible to its parts were intense in the German speaking psychologi- cal world, started by Christian von Ehrenfels in 1890 and actively ­participated in by many (best overview in Brunswik, 1929). Under different labels—Fundierte Inhalt or Komplex, aside from various meaning of Gestalt, these discussions provided a basis for at least four different perspectives cen- tered on the notion of the whole in the human psyche, to proliferate. 4 Interestingly, Köhler himself rarely mentions the history of captivity of the chimpanzees in Tenerife prior to their arrival in 1913, nor does he put much emphasis on the reha- bilitation efforts that went on under Eugen Teuber’s super- vision in the course of 1913 (see p. 205 in this book—focus on the absence of objects in the “narrowest cages” in which they were taken from Cameroon and Nigeria to Tenerife). He needed to prove the pre-experimental lack of experience with the specific objects, rather than consider the possibility that the experiences in captivity had detrimentally altered the mental orientations of the apes. 5 Hans-Lukas Teuber (1916–1977) grew up to become an innovative neuroscientist at MIT http://www.nap.edu/ read/1000/chapter/18#473. 6 The phenomenon of insight (Einsicht or “Aha-Erlebnis”) was discovered by Karl Bühler in human introspection experiments (Bühler, 1907, 1951). It involves a rapid synth- sis of a solution to a problem, or a “jump” in meaningful understanding, in a problem situation. Köhler carried the notion to Tenerife and created experimental conditions where it could be observed behaviorally in chimpanzees. For him, insight was a rapid transformation of the field structure, as a descriptive term (Köhler, 1947, p. 200). 7 Which William Stern (1935) found to be the main limit of the Berlin Gestalt tradition—the organization of the field The place of innovation in the lives of apes xxxv

was claimed to take place without active and purposeful role of the agent. 8 Köhler clearly understood that chipanzees could take the perspective of the Other: “I was endeavouring to teach Chica the use of the double stick. I stood outside the bars, Sultan squatted on my side, and gazed seriously, slowly scratching his head meanwhile. As Chica absolutely failed to real- ize what was required, I finally gave the two sticks to Sultan, in the hope that he would make the things clear. He took the sticks, fitted one into the other, and did not himself appropriate the fruit, but pushed it, in a leisurely manner, towards Chica at the bars” (p. 172, added emphases). Köhler commented upon the importance that Sultan was not hungry at the moment. Keeping animals fed—or ­starving them before experiments—has been an accepted contrast for animal researchers who try to study learning by animals. Apparently the emergence of teaching depends on the non-hungry state of the animal. The need worldwide to pay teachers reasonable salaries seems anticipated at the level of higher primates! 9 Ladders were of course in use—but these were solidly stand- ing on the ground. When given to chimpanzees as possible implements the chimpanzees would use these as poles, not as ladders (pp. xxxi). 10 Idioadaptations in the terminology of Alexei Severtsov (Swertzoff, 1929) are new forms of behavior or bodily func- tions that emerge under the demands of the environment, and would not be retained as practices after the demands end (the ones that are retained are aromorphoses). Most if not all of the innovations Köhler’s experiments triggered are of such kind. 11 It should not be forgotten that the Tenerife station was a “half-way house” between Africa and Berlin Zoo. As has been usual in zoos and laboratories the material envi- ronment of the animals is strategically controlled to avoid accidents. Any modification of such impoverished environ- ments can bring back behavioral tactics from the past in the rich natural environments. Re-arrangements made in xxxvi The Mentality of Apes

the demand structures of the impoverished field conditions may under some conditions lead to remarkable adaptations­ to the human-made settings (Savage-Rumbaugh, Shanker and Taylor, 1998; Sagerdahl, Fields, and Savage- Rumbaugh, 2005). In contrast, “full” natural environ- ments of primates (e.g. Boesch and Boesch-Achermann, 2000; Stanford, 2008) in the wild have been shown to lead to a variety of tool-making and -using local traditions (Matsuzawa, Humle, and Sugiyama, 2011; McGrew, 1992; Reynolds, 2005). 12 Nut cracking with stone tools has been demonstrated to be 2000–4000 years old in archeological findings. Over 200 generations of chimpanzees have transferred that ­tool-using skill on to the present day (Boesch, 2012, p. 683).

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1. Two sets of interests lead us to test the intelligence of the higher apes. We are aware that it is a question of beings which in many ways are nearer to man than to the other ape species; in particular it has been shown that the chemistry of their bodies, in so far as it may be perceived in the quality of the blood, and the structure of their most highly-developed organ, the brain, are more closely related to the chemistry of the human body and human brain-structure than to the chemical nature of the lower apes and their brain development. These beings show so many human traits in their “everyday” behav- iour that the question naturally arises whether they do not behave with intelligence and insight under conditions which require such behaviour. This question expresses the first, one may say, naive, interest in the intellectual capacity of animals. We wished to ascertain the degree of relationship between anthropoid apes and man in a field which seems to us particularly important, but on which we have as yet little information. The second aim is theoretical. Even assuming that the unthropoid ape behaves intelligently in the sense in which the word is applied to man, there is yet from the very start no doubt that he remains in this respect far behind man, 2 The Mentality of Apes becoming perplexed and making mistakes in relatively simple situations; but it is precisely for this reason that we may, under the simplest conditions, gain knowledge of the nature of intelligent acts. The human adult seldom performs for the first time in his life tasks involving intel- ligence of so simple a nature that they can be easily inves- tigated; and when in more complicated tasks adult men really find a solution, they can only with difficulty observe their own procedure. So one may be allowed the expecta- tion that in the intelligent performances of anthropoid apes we may see once more in their plastic state processes with which we have become so familiar that we can no longer immediately recognize their original form: but which, because of their very simplicity, we should treat as the logical starting-point of theoretical speculation. As all the emphasis in the following investigations is laid on the first question, the doubt may be expressed whether it does not take for granted a particular solution of the problems treated under the second. One might say that the question whether intelligent behaviour exists among anthropoid apes can be discussed only after recognizing the theoretical necessity of distinguishing between intel- ligent behaviour and behaviour of any other kind; and that, since association psychology, in particular, claims to derive from one single principle all behaviour which would come under consideration here, up to the highest level, even that attained by human beings, a theoretical point of view is already assumed by the formulation of problem 1; and one which is antagonistic to association psychology. This is a misconception. There is probably no asso- ciation psychologist who does not, in his own unpreju- diced observations, distinguish, and, to a certain extent, contrast, unintelligent and intelligent behaviour. For what is association psychology but the theory that one Introduction 3 can trace back to the phenomena of a generally-known simple association type even those occurrences which, to unbiased observation, do not at first seem corresponding to that type, most of all the so-called intelligent perfor- mances? In short, it is just these differences which are the starting-point of a strict association psychology; it is they which need to be theoretically accounted for; they are well known to the association psychologist. Thus, for instance, we find a radical representative of this school (Thorndike) stating the conclusion, drawn from experi- ments on dogs and cats: “I failed to find any act that even seemed due to reasoning.” To anyone who can formulate his results thus, other behaviour must have seemed to be intelligent; he is already acquainted with the contrast in his observations, say of human beings, even if he discards it afterwards in theory. Accordingly, if we are to inquire whether the anthro- poid ape behaves intelligently, this problem can for the present be treated quite independently of theoretical assumptions, particularly those for or against the asso- ciation theory. It is true that it then becomes somewhat indefinite; we are not to inquire whether anthropoid apes show something well defined, but whether their behav- iour approximates to a type rather superficially known by experience, and which we call “intelligent”1 in con- trast to other behaviour—especially in animals. But in proceeding thus, we are only dealing according to the nature of the subject; for clear definitions have no place at the beginning of sciences founded on experience; it is only as we advance towards results that we can mark our progress by the formulation of definitions. Moreover, the type of human and, perhaps, animal behaviour to which the first question animadverts is not quite indefinite, even without a theory. As experience shows, we do not speak of behaviour as being intelligent, 4 The Mentality of Apes when human beings or animals attain their objective by a direct unquestionable route which clearly arises naturally out of their organization. But we tend to speak of “intel- ligence” when, circumstances having blocked the obvious course, the human being or animal takes a roundabout path, so meeting the situation. In unexpressed agreement with this, nearly all those observers who heretofore have sought to solve the problem of animal intelligence, have done so by watching animals in just such predicaments. Since animals below the stage of development of anthro- poid apes give, in general, negative results, there has arisen out of these experiments the view widely held at present, i.e., that there is very little intelligent behaviour in animals. Only a small number of such experiments have been carried out on anthropoid apes, and they have not yet produced any very definite results. All the experi- ments described in the following pages are of one and the same kind: the experimenter sets up a situation in which the direct path to the objective is blocked, but a roundabout way left open. The animal is introduced into this situation, which can, potentially, be wholly surveyed. So we can see of what levels of behaviour it is capable, and, particularly, whether it can solve the problem in the possible “roundabout” way. 2. The experiments were at first applied to chimpanzees only, with the exception of a few cases taken for com- parison, in which human beings, a dog, and hens were observed. Seven of the animals belonged to the old branch of the anthropoid station which the Prussian Academy of Science maintained in Tenerife from 1912 to 1920. Of these seven the oldest, an adult female, was named Tschego, because of several characteristics which made us, perhaps wrongly, consider her a member of the Tschego species. (We are yet far from possessing a clear Introduction 5 and systematized classification of the varieties of the chimpanzee.) The oldest of the smaller animals, called Grande, differed considerably in several respects from its comrades. But as the differences concern its general character rather than the behaviour investigated in the intelligence tests, a detailed description of them would be out of place here. The other five, two males (Sultan and Konsul), and three females (Tercera, Rana, and Chica), were of the usual chimpanzee type. To the seven animals mentioned, two others were added later, both of which led to valuable observations, but both of which, to our regret, soon died. I shall briefly describe them in order to give an impression of the completely different “personalities” which exist among chimpanzees. Nueva, a female ape, about the same age as the other little animals (four to seven years at the time of the majority of our experiments), differed from them bodily in her extraordinarily broad ugly face and an obviously pathological sparsity of hair on her unhealthy skin. But her ugliness was completely offset by a nature so mild and friendly, of such naïve confidence and quiet clarity as never fell to our lot to meet with in a chimpanzee before or after. Her childlike attachment we found to some extent in other animals when they were ill, and perhaps many of Nueva’s good qualities can be explained by the fact that, from the beginning, she was the prey of a slowly-advancing disease; chimpanzees, on the whole, can do with a little suppression. We were particularly impressed by the way she would play for hours, quite contentedly, with the simplest toys. Unfortunately the others tended to become lazy if they were not given any particular employment, or if they were not quarrel- ling, or inspecting each other’s bodies. If a number of healthy children are left together all the time, without any 6 The Mentality of Apes particular occupation, the effect will not be in the line of a discreet, though playful activity either. Nueva had been kept alone for many months. One must, however, not assume that the pleasant qualities of this animal were due to earlier educational influences. Unfortunately, educa- tion does not seem able to transform a naturally mis- chievous and wanton chimpanzee into an amiable being; moreover, Nueva was not “brought up” in the nursery sense; on the contrary, she showed that she was not used to being corrected at all. She regularly ate her excretions, and was first astonished and then extremely indignant when we took measures against this habit. On the second day of her stay at the station, the keeper threatened her, during this proceeding, with a little stick, but she did not understand the meaning of the stick, and wanted to play with it. If food which she had, with complete naiveté, appropriated somewhere, was taken away from her she would bite, in her sudden rage, immediately; she was as yet without any inhibitions towards man; in fact, she showed herself completely naïve, and was, without doubt, less “cultured” than the station animals. The male, Koko, judged to be about three years of age, was a type of chimpanzee not uncommonly met with: above his drum-taut stomach a pretty face with neatly parted hair, a pointed chin, and prominent eyes which seemed always discontentedly asking for something, giving the little fellow a native expression of sauciness. A large part of his existence was, in fact, spent in a kind of chronic indignation, either because there was not enough to eat, or because the children came too near him, or because someone who had just been with him left him again, or finally, because he could not remember to-day how he had solved a similar test yesterday. He would not complain; he would merely be indignant. Usually this mood was manifested by loud pommelling on the floor Introduction 7 with both fists, and an agitated hopping up and down in one spot; in cases of great rage by glottal cramp-attacks which passed over quickly. (These we noticed also in other chimpanzees when they had attacks of rage, and very rarely in manifestations of joy.) Before such attacks, and in cases of minor excitement, he would utter a con- tinual staccato ŏ in that irregular characteristic rhythm which one hears from a slow-firing line of soldiers. In his angrily-uttered demands, and his wild indignation if they were not immediately satisfied, Koko resembled another egoist par excellence, Sultan. Luckily—and perhaps that is no accident —Koko was, at the same time, just as gifted as Sultan. These are only two chimpanzees. For one who has seen Koko and Nueva alive, there is no doubt that in their own way they were as much unlike as two human chil- dren with fundamentally different characters, and one can set up as a general maxim that observations of one chimpanzee should never be considered typical for all of this species of animal. The experiments we describe in the following show that there are just as great individual differences in the intellectual field. Practically all the observations were made in the first six months of 1914.2 They were frequently repeated later, but only a few additional experiments and repetitions (dating from the spring of 1916) are incorporated in this report, as, in general, the behaviour observed the first time was repeated; in any case, no important corrections had to be made in the earlier results. 3. Experiments of the kind described above may make very different calls upon the animals to be tested, accord- ing to the situation in which they are put. In order to discover, even roughly, the zone of difficulty within which the testing of chimpanzees will be of any use, Mr. E. Teuber and I gave them a problem which seemed to us 8 The Mentality of Apes difficult, but not impossible, of solution for a chimpan- zee. How Sultan behaved in this test should be sketched here as a preliminary example. A long thin string is tied to the handle of a little open basket containing fruit; an iron ring is hung in the wire- roof of the animals’ playground through which the string is pulled till the basket hangs about two metres above the ground; the free end of the string, tied into a wide open loop, is laid over the stump of a tree-branch about three metres away from the basket, and about the same height from the ground; the string forms an acute angle—the bend being at the iron ring (cf. Fig. 1). Sultan, who has not seen the preparations, but who knows the basket well from his feeding-times, is let into the playground while the observer takes his place outside the bars. The animal looks at the hanging basket, and soon shows signs of lively agitation (on account of his unwonted isolation), thunders, in true chimpanzee style, with his feet against a wooden wall, and tries to get into touch with the other animals at the windows of the ape-house and wherever there is an outlook, and also with the observer at the bars; but the animals are out of sight, and the observer remains

Fig. 1. Introduction 9 indifferent. After a time, Sultan suddenly makes for the tree, climbs quickly up to the loop, stops a moment, then, watching the basket, pulls the string till the basket bumps against the ring (at the roof), lets it go again, pulls a second time more vigorously so that the basket turns over, and a banana falls out. He comes down, takes the fruit, gets up again, and now pulls so violently that the string breaks, and the whole basket falls. He clambers down, takes the basket, and goes off to eat the fruit. Three days later, the same experiment is repeated, except that the loop is replaced by an iron ring at the end of the rope, and the ring, instead of being put over the branch, is hung on a nail driven into a scaffolding (used for the animals’ gymnastics). Sultan now shows himself free from all doubt, looks up at the basket an instant, goes straight up to the scaffolding, climbs it, pulls once at the cord, and lets it slip back, pulls again with all his might so that the cord breaks, then he clambers down, and fetches his fruit. The best solution of the problem which could be expected would be that the animal should take the loop or iron ring off the branch or nail and simply let the basket drop, etc. The actual behaviour of the animal shows plainly that the hub of the situation, i.e., the rope connexion, is grasped as a matter of course, but the fur- ther course of action for the experiment is not very clear. The best solution is not even indicated. One cannot tell just why. Did Sultan perhaps not see the loose fixing of the loop to the branch or ring to the nail? If he had noticed it, would he have been able to solve it? Would he in any case expect the basket to fall to the ground if this fastening were loosened? Or does the difficulty lie in the fact that the basket would fall to the ground, and not straight into Sultan’s hands? For we cannot even know whether Sultan really pulled at the cord to break it, and 10 The Mentality of Apes thus bring the basket to earth. So we have performed one experiment which, for a beginning, contains conditions too complicated to teach us much, and, therefore, we see the necessity of beginning the next examinations with elementary problems in which, if possible, the animals’ conduct can have one meaning only.

Notes 1 See foot-note, p. 219. 2 That is, they were made before the chimpanzees underwent optical examination. (Cf. these in the Abh. d. Kgl. Preuss. Akd. d. Wiss, 1915, Phys.-Math. Section No. 3.)