Classics in the History of Psychology

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Christopher D. Green
York University, Toronto, Ontario

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Introduction to

Animal Intelligence
Edward Lee Thorndike (1911)

Robert H. Wozniak

© 1999 Robert H. Wozniak. All rights reserved. Previously published in Wozniak, R. H. (1999). Classics in Psychology, 1855-1914: Historical Essays. Bristol, UK: Thoemmes Press. Reprinted by permission of the author.

Between 1898 and 1901, Edward Lee Thorndike[1] published two major research monographs and several shorter articles that established the study of animal learning as a laboratory science. As he himself put it, this work marked a '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.'[2]

A decade or so later, in 1911, Thorndike brought these early studies together in a single volume. Adding an introduction arguing for the importance of studying behavior in its own right and a theoretical chapter on 'laws and hypotheses of behavior,' he entitled the new work, Animal Intelligence: Experimental Studies.

By far the most important section of the new volume consisted of a reprint of Thorndike's dissertation of 1898. This dissertation, also entitled Animal Intelligence, but subtitled, An Experimental Study of the Associative Processes in Animals,[3] is widely considered to be one of the most influential publications of the first half century of psychological science. In addition to offering a conception of animal intelligence couched solely in terms of the organism's ability to form new associations, it described ingenious apparatus for the observation of animal learning and demonstrated the use of such apparatus in systematic laboratory research.

Although not as well known or as influential as Thorndike's dissertation, The Mental Life of Monkeys,[4] also reprinted in Animal Intelligence, is another monograph of considerable interest. Starting from the hypothesis that rational thought and ideation in humans was merely an extension of animal intelligence, that concepts, feelings of relationship, association by similarity, and even reason itself followed from a simple increase in the number, delicacy, and complexity of associations, Thorndike examined the learning curve in monkeys for evidence of ability to learn by imitation or by inference. Despite finding marked differences in learning between monkeys and cats and dogs, Thorndike concluded that there was little support for the claim that monkeys were capable of either imitation or reasoning.

In both of these monographs and in more minor papers on behavior in young chicks and in fishes also included in Animal Intelligence, Thorndike situated himself theoretically within the long tradition of associationism. Unlike his associationist predecessors, however, he construed association not as linking one idea or element of consciousness with another nor even as linking ideas with movements. Rather, for Thorndike, associations exist between situations in which an organism finds itself and impulses in the organism to action. In this regard, Thorndike took a step beyond traditional associationism in the direction of the stimulus-response approach that would eventually come to dominate the field.

In this work, Thorndike was also a methodological innovator, developing a general experimental technique that was to revolutionize the psychological study of animal behavior. As described by a prominent modern researcher, Thorndike's approach to method 'was objective: it minimized the influence of the observer...quantitative: the course of learning could be measured accurately in terms of the time taken for the appearance of the correct response on each trial...reproducible: the work of one investigator could be repeated and verified by others...flexible: the responses required could be varied in kind and complexity...natural:...the problems presented...were not too remote from the animal's ordinary course of life...(and) convenient: a large enough sample of animals could be studied to provide a representative picture of each of a variety of species.'[5]

Finally, the new sections of Animal Intelligence -- Thorndike's introductory apology for the study of behavior and his chapter on 'laws and hypotheses of behavior' -- were also innovative. In his introduction to the book, Thorndike defended two propositions. The first, that psychology could be viewed as the science of behavior continuous with physiology, anticipated arguments soon to be advanced by John B. Watson in his famous behaviorist manifesto.[6] The second, that the study of 'consciousness for the sake of inferring what a man can or will do, is as proper as to study behavior for the sake of inferring what conscious states he can or will have,'[7] anticipated the general approach to consciousness that would become common among early behaviorists.[8]

In the chapter on 'laws and hypotheses of behavior,' Thorndike first discussed 'effect' and 'exercise' as provisional laws of acquired behavior. Then, focusing on the phylogenesis of intellectual and moral behavior as an example, he attempted to show how acceptance of these laws facilitated the analysis of problems related to learning. In both respects, this essay foreshadowed the more extensive analysis of learning principles that Thorndike himself was to provide in his Educational Psychology.[9]


[1] 1874-1949. For biographical information on Thorndike, see Joncich, G. (1968). The Sane Positivist: A Biography of Edward L. Thorndike. Middletown, CT: Wesleyan University Press.

[2] Thorndike, E. L. (1911). Animal Intelligence. New York: Macmillan (Reprinted Bristol:Thoemmes, 1999), p. v.

[3] Thorndike, E. L. (1898). Animal Intelligence: An Experimental Study of the Associative Processes in Animals (Psychological Review, Monograph Supplements, No. 8). New York: Macmillan.

[4] Thorndike, E. L. (1901). The Mental Life of the Monkeys (Psychological Review, Monograph Supplements, No. 15). New York: Macmillan.

[5] Bitterman, M.E. (1969). Thorndike and the problem of animal intelligence. American Psychologist, 24, 444-53.

[6] Watson, J. B. (1913). Psychology as the behaviorist views it. Psychological Review, 20, 158-77.

[7] Thorndike (1911), op. cit., p. 5.

[8] Wozniak, R. H. (1994). Behaviourism: The early years. In R.H. Wozniak (Ed.). Reflex, Habit and Implicit Response: The Early Elaboration of Theoretical and Methodological Behaviourism. London: Routledge/Thoemmes Press, pp. ix-xxxii.

[9] Thorndike, E. L. (1914). Educational Psychology: Briefer Course. New York: Teachers College, Columbia University.