The following text is © 1997 Robert Wozniak. All hyperlinked text links to footnotes located at the bottom of the document.

Conwy Lloyd Morgan, Mental Evolution, and The Introduction to Comparative Psychology

Robert H. Wozniak
Bryn Mawr College

C. Lloyd Morgan's (1852-1936) Introduction to Comparative Psychology, first published in 1894 and revised nine years later[1], is now known almost exclusively for thirty-six famous words. Discussing problems in the interpretation of animal behavior, Morgan wrote that:

"In no case may we interpret an action as the outcome of the exercise of a higher psychical faculty, if it can be interpreted as the outcome of one which stands lower in the psychological scale."[2]

This principle, widely known as Morgan's Canon, played a conspicuous role in justifications of anti-mentalism during the reigning years of behaviorism. Indeed, as psychologists recapitulated Morgan's views during this period, his Canon began to sound more and more like the creed of an arch behaviorist. In 1938, for example, B.F. Skinner (1904-1990) informed his readers that "Darwin, insisting upon the continuity of mind, attributed mental faculties to subhuman species. Lloyd Morgan, with his law of parsimony, dispensed with them in a reasonably successful attempt to account for characteristic animal behavior without them."


A few years later, Coleman Griffith (1893-1966) described "Morgan's appeal to the principle of parsimony"[4] in the following way:

"In Morgan's case, the principle amounted to this. Where there is a pattern of animal behavior which must be explained, both as to form and to origin, and in the simplest, but at the same time, most adequate way, the experimenter should appeal to factors observable in the situation in which the animal has been placed, in the behavior itself, and in the machinery by which the behavior is made possible. It is not incumbent on him to pass over these factors in order to appeal to a verbal construct, to a mind, or to any other kind of mental factor which lies outside of, behind, or within the behavior-situation." [5]

Finally, in 1947, Philip L. Harriman (1894-1968), in his New Dictionary of Psychology[6], went so far as to identify Morgan's Canon with the law of parsimony:

"Parsimony, law of: Lloyd Morgan's statement (1900) that animal behavior should be described in the simplest possible terms. It is an application of Occam's razor to animal psychology. Occam (1280-1349) had said that entities must not be multiplied beyond necessity; and Morgan accepted this view, indicating that anecdotes, attribution of human mental activities to animals, and projection of introspections have no place in animal psychology."

One thing is virtually certain -- neither Skinner, nor Griffith, nor Harriman could ever have read Lloyd Morgan. Even if one set out deliberately to distort the meaning of Morgan's Canon, it would be virtually impossible to do so with greater success. Morgan's Canon is not a principle of parsimony,[8] it was not formulated as a guide to the description of behavior, it does not dispense with mental faculties, it is not an appeal to the observable, and it is not meant to be specific to animal psychology. Even worse, it is consciously anthropomorphic and based squarely on the adequacy of the psychologist's personal introspection.

Within the broad context of Morgan's approach to the study of mental evolution and his concern with limitations on the psychologist's ability to know other minds, the famous Canon is best read as an admonition to psychologists to know their own minds. For Morgan, mind is consciousness. Psychical states are states of conscious experience. Scientists who wish to understand the conscious experience of animals can do so only by analogy to their own mental processes.

The basis for this view is Morgan's assumption that the hierarchical organization of human consciousness is the outcome of an evolutionary process at least partially shared with lower organisms. On this assumption, human consciousness contains multiple levels of psychical organization. Certain of these levels can provide a more or less adequate basis for analogical inference concerning the nature of animal consciousness. To prosecute such analogies successfully, however, the psychologist must satisfy two requirements.

The first requirement, which Morgan did not formalize, might be called the principle of adequate introspection. According to this principle, psychologists must be sufficiently skilled in analytic introspection that they can distinguish higher from lower psychical organizations within the flow of their own conscious processes. As Morgan puts it:

"It will thus be seen that in studying other minds through their objective manifestations, it is primarily essential that we should have, so far as is possible, a thorough and accurate acquaintance with the only mind we can study at first-hand and directly, namely our own. Without this, anything like scientific interpretation is manifestly impossible...the first duty of a psychologist is to attain accurate and systematic acquaintance with the working of his own mind, as the cipher in terms of which all other minds must be read..."

The second requirement, which Morgan did formalize, is his famous Canon. In the context of Morgan's overall argument, it is clear that the intent of the Canon was to provide psychologists with a guide to the use of their own introspections. Rephrased to emphasize this function, it might just as easily have been stated as follows: "In employing the results of personal introspection to draw analogical inferences about the nature of animal mind, the psychologist must strictly avoid interpreting an animal's actions in terms of his or her own higher psychical processes (e.g., reasoning) when lower processes (e.g., simple association of ideas) may be sufficient."

This a far cry from behaviorism,[10] and John B. Watson (1878-1958), titular founder of behaviorism, would have been the first to dissociate himself from the real Canon of Lloyd Morgan. Indeed, Watson's own comparative psychology text of 1914, Behavior: An Introduction to Comparative Psychology,[11] carries only a single somewhat disparaging reference to Morgan[12] and ignores Morgan's Canon.

Yet Morgan's text is of fundamental importance in the history of behaviorism. This is true for two quite different reasons. First, behaviorism has its deepest roots in the comparative psychology of animal behavior, and it is Morgan's text that defined what it meant to be a comparative psychologist. While Herbert Spencer (1820-1903)[13], Charles Darwin (1809-1882),[14] and George John Romanes (1848-1894)[15] fashioned a conception of mental evolution that lay the groundwork for the comparative study of mind, Morgan gave comparative psychology the status of science.

In the Introduction to Comparative Psychology, Morgan was self-reflective about his assumptive base[16] and explicit about the general requirements of method.[17] As he put it, the problems of comparative psychology "will have to be settled, if...(they) can be settled at all, not by any number of anecdotes, -- interesting, and to some extent valuable, as such anecdotes are, -- but by carefully conducted experimental observations, carried out as far as possible under nicely controlled conditions."[18] In this regard, Morgan stood mid-way between the anecdotalism of Romanes' 1883 Animal Intelligence,[19] widely considered to be the first comparative psychology, and the laboratory experimentalism of Robert M. Yerkes (1876-1956) and of J. B. Watson, whose 1911 Methods of Studying Vision in Animals[20] established a methodological standard for the objective study of animal behavior.

Morgan's Introduction is of critical importance in the history of behaviorism for another, very different reason. It was comparative psychology in the Morgan mold against which Watson's behaviorist polemics were directed. It is Morgan who was concerned with the subjective character of animal mind, who required careful introspection on the part of the animal psychologist, and for whom the scientific value of comparative psychology's data was "dependent upon the readiness with which they [the data] lend themselves to interpretation in terms of consciousness."[21]

More importantly, Morgan's text is itself a masterpiece. It is coherent, programmatic, and uncompromising in its pursuit of animal mind within the framework of mental evolution. It is, in effect, the best and most comprehensive statement of the type of psychology that Watson had in mind when he called for a revolution. Indeed, without the context provided by Morgan's Introduction, it may be impossible to appreciate fully the point of Watson's call to arms . In this light, it is of interest to look at Morgan's own personal and intellectual background.

Conwy Lloyd Morgan was born in London in 1852[22]. The son of a solicitor, Morgan received a traditional, mid-19th century English grammar school education at the Royal Grammar School in Guildford. Toward the end of his school days, he was introduced to Bishop George Berkeley's (1685-1753) Treatise concerning the Principles of Human Knowledge[23] by his parish rector, at whose urging Morgan also tackled Locke, Descartes, Hume, and Reid among others.

Although Morgan eventually adopted a dual-aspect monist position on the relationship between the objective and subjective in experience and between mind and brain,[24] Bishop Berkeley's immaterialism exerted a life-long but subtle influence on Morgan's views. In this regard, one is tempted to ascribe Morgan's tendency to equate mind with conscious experience, his dogged commitment to the relative solipsism of personal experience, and his consequent concern with the problem of other minds to his adolescent exposure to the good Bishop.

After Morgan's graduation from grammar school, on the advice of family and friends, but with little enthusiasm, he entered the London School of Mines in the Royal College of Science to study for a degree in mining and metallurgy. Although he performed brilliantly and finished first in his graduating class, by the time he completed his course of study whatever slight interest he had had in mining as a profession had long since evaporated.

Just at that time, Morgan was asked to serve as chair for the annual student/staff dinner. In this position, he found himself sitting next to the Royal College of Science Professor of Natural History, Thomas Henry Huxley (1825-1895), the great defender of Darwinism. As Morgan himself described the evening:

"[Huxley] courteously sounded me on my aims and prospects. I...touched on my interest in Berkeley, and lamented my ignorance of biology. In the intervals between speeches he returned to the topic; gave me of his riches without emphasizing my poverty. And, as he bade me a kindly 'Good-night,' suggested that, if it was possible, I might as well put in a year under him."[25]

Immediately after graduation, Morgan journeyed to North America for three months as traveling tutor to the son of a wealthy Chicago family. With leisure to read, he made his way through both the Origin of Species[26] and the Descent of Man[27], and returned to England to take Huxley up on his offer. At the conclusion of his year with Huxley, Morgan plunged into the task of making a living, working some as an assayer for a mining company, some as a part-time private school science teacher.

In 1878, determined to try his hand at full-time teaching, Morgan accepted a position at the Diocesan College at Rondebosch, near Cape Town, South Africa. In the five years spent at the Cape, he continued to read philosophy and managed to complete several manuscripts, including "Animal intelligence,"[28] an article in Nature critical of Romanes' attribution of abstract ideas to dogs, and The Springs of Conduct; An Essay in Evolution,[29] a book-length discussion of issues relating to the possibility of a comparative psychology. In The Springs of Conduct, in an unpublished paper entitled Mental Evolution in Animals[30] written about 1883, and in a short paper, Instinct,[31] published in 1884, Morgan dismissed the possibility of a science of comparative psychology of the type envisioned by Romanes.

Under the continuing influence of Berkeley and the problem of other minds, Morgan pointed to the fact that only the knowledge of our own psychical states is direct. Knowledge of other minds is always and only by " ejective"[32] analogy to our own. In the case of other adult humans, who possess language, who can inform us of their thoughts and feelings, and who are in some measure similar to ourselves, our analogies are likely to be valid and can be subjected to verification. Animals, on the other hand, have minds that are radically different from our own and lack any language by which to communicate their mental states. On these grounds, no scientific knowledge of animal mind is possible.

In 1884, shortly after his return to England, Morgan received an appointment as a professor of geology and zoology (eventually psychology and ethics) at University College Bristol, where he remained until his retirement in 1920, assuming the Principalship in 1887 and serving briefly as Vice Chancellor when University College became the University of Bristol in 1909. After the turn of the century, Morgan's interests turned increasingly toward philosophy and problems in the concept of emergent evolution.[33]

Between 1885 and 1900, however, the period with which we are chiefly concerned, Morgan published a number of experimental studies of animal behavior[34]and worked out the general monistic rationale[35] which led him to abandon his earlier opposition to a comparative psychology of mental evoluution. This series of developments culminated in the Introduction to Comparative Psychology published with its famous Canon in 1894. As Costall has aptly described Morgan's enunciation of the Canon:

"Far from being a "revolt" against Romanes, it was a fundamental, if unacknowledged, concession. It was a statement of his new conviction in the possibility of the study of mental evolution, and, as such, was clearly an acceptance of Romanes's conception of a true comparative psychology, as opposed to a mere study of animal conduct."

Yet it was just precisely the "mere study of animal conduct," shorn of the anthropomorphism inherent in the intent of Morgan's Canon and divorced from introspection as method, that constituted the new behaviorism of John B. Watson. By focusing on the problem of method, clarifying the assumptive base of an evolutionary psychology of comparative mental processes, and eschewing anecdotal evidence, Morgan defined the field that Watson set out to revolutionize.


1. Morgan, C.L. (1903). Introduction to comparative psychology. London: Walter Scott (2nd edition, revised). In the belief that the revised form of Morgan's work would have been the edition most readily available to those working in animal behavior when Watson articulated his behaviorist program [Watson, J.B. (1913). Psychology as the behaviorist views it. Psychological Review, 20, 158-177], we have chosen to reprint the edition of 1903 rather than the first edition of 1894. [Back to text]

2. Ibid., p. 53. [unchanged from the edition of 1894]. [Back to text]

3. Skinner, B.F. (1938). Behavior of organisms. NY: Appleton-Century, p. 4. [Back to text]

4. Griffith, C.R. (1943). Principles of systematic psychology. Urbana, IL: University of Illinois Press, p. 322. [Back to text]

5. Ibid. [Back to text]

6. Harriman, P.L. (1947). The new dictionary of psychology. NY: Philosophical Library. [Back to text]

7. Ibid., p. 255. [Back to text]

8. It would be an interesting study in itself to trace the progressive distortion of Morgan's views and in particular the attribution to Morgan of the principle of parsimony. Although earlier writings may also have misinterpreted Morgan in this fashion, it seems likely that Boring [Boring, E.G. (1929). A history of experimental psychology. NY: Century.] was one of the more influential culprits. See especially pp. 464-465. [Back to text]

9. Morgan, C.L. (1903), pp. 44-45. [unchanged from the first edition of 1894]. [Back to text]

10. Over the past 60 years, the persistent misinterpretation of Morgan's Canon has been the subject of sporadic commentary [Nagge, J.W. (1932). Regarding the law of parsimony. Journal of Genetic Psychology, 41, 492-494; Newbury, E. (1954). Current interpretation and significance of Lloyd Morgan's Canon. Psychological Bulletin, 51, 70-74; Burghardt, G.M. (1985). Animal awareness: Current perceptions and historical perspective. American Psychologist, 40, 905-919; Costall, A. (1993). How Lloyd Morgan's Canon backfired. Journal of the History of the Behavioral Sciences, 29, 113-122] -- all seemingly to no avail. [Back to text]

11. Watson, J.B. (1914). Behavior: An introduction to comparative psychology. NY: Henry Holt. [Back to text]

12. Ibid., p. 278: "Examination of the literature shows that experimenters have usually chosen some anthropomorphic type of classification of imitation, such as that outlined by Morgan..." [Back to text]

13. Spencer, H. (1855). The principles of psychology. London: Longman, Brown, Green, and Longmans. [Back to text]

14. Darwin, C. (1871). The descent of man, and selection in relation to sex. London: John Murray. [Back to text]

15. Romanes, G.J. (1883). Mental evolution in animals. London: Kegan Paul, Trench & Co.; and Romanes, G.J. (1888). Mental evolution in man: Origin of human faculty. London: Kegan Paul, Trench & Co. [Back to text]

16. Morgan (1903), see "Prolegomena," pp. 1-10. [pagination unchanged from the edition of 1894]. [Back to text]

17. Ibid., see "Other minds than ours," pp. 36-59. [pagination unchanged from the edition of 1894]. [Back to text]

18. Ibid., p. 363 [p. 359 in the edition of 1894]. [Back to text]

19. Romanes, G.J. (1882). Animal intelligence. London: Kegan Paul, Trench & Co. [Back to text]

20. Yerkes, R.M. & Watson, J.B. (1911). Methods of studying vision in animals. Boston: Henry Holt & Co. [Behavior Monographs, Serial Number 2.] [Back to text]

21. Watson (1913), p. 158. [Back to text]

22. Biographical details of Morgan's life have been drawn from: Morgan, C.L. (1932). C. Lloyd Morgan. In C. Murchison (Ed). A history of psychology in autobiography. Volume II. Worcester, MA: Clark University Press, pp. 237-264; Grindley, G.C. (1936). Obituary notice: Professor C. Lloyd Morgan, 1852-1936. The British Journal of Psychology. General Section, 27, 1-3; and Richards, R.J. (1987). Darwin and the emergence of evolutionary theories of mind and behavior. Chicago: University of Chicago Press, especially pp. 375-404. [Back to text]

23. Berkeley, G. (1710). A treatise concerning the principles of human knowledge...Dublin: Printed by Aaron Rhames for Jeremy Pepyat. [Back to text]

24. Morgan (1903), pp. 1-10. [pagination unchanged from the edition of 1894]. Morgan's monism quite clearly reflects the influence of George Henry Lewes (1817-1878) [Lewes, G.H. (1877). The physical basis of mind. With illustrations. Being the second series of Problems of life and mind. London: Trčbner & Co.] For a discussion of Lewes' dual-aspect monism, see: Wozniak, R.H. (1992). Mind and body: RenÄ Descartes to William James. Bethesda, MD: National Library of Medicine and Washington, D.C.: American Psychological Association. [Back to text]

25. Morgan (1932), p. 241. [Back to text]

[Back to text] 26. Darwin, C. (1859). On the origin of the species by means of natural selection, or, The preservation of favoured races in the struggle for life. London: John Murray.

27. Darwin, C. (1871). [Back to text]

28. Morgan, C.L. (1882). Animal intelligence. Nature, 26, 523-524. [Back to text]

29. Morgan, C.L. (1885). The springs of conduct; An essay in evolution. London: Kegan Paul, Trench. [Back to text]

30. See Richards (1987), pp. 377-379 for an excellent discussion of the contents of this paper, which is located in the C. Lloyd Morgan Papers, DM 612, University College Library, Bristol. [Back to text]

31. Morgan, C.L. (1884). Instinct. Nature, 29, 370-374, 405, 451-452. [Back to text]

32. Ibid., p. 370: "an image of my own mind thrown out from myself." [Back to text]

33. Morgan (1932), pp. 251-264. [Back to text]

34. See, for example, Morgan, C.L. (1887). The beetle in motion. Nature, 35, 7; Morgan, C.L. (1893). Observations on ducklings. Science, 22, 63-64; Morgan, C.L. (1894). Observations on young pheasants. Nature, 50, 575-576; Morgan, C.L. (1896). The habit of drinking in young chicks. Science, 3, 900; and Morgan, C.L. (1900). Instinct vs. experience in newly hatched chicks. Nature, 62, 590. [Back to text]

35. Morgan, C.L. (1885). On the study of animal intelligence. [An unpublished lecture delivered to the Bristol Naturalists Society on the 1st of October, 1885, in the papers of C. Lloyd Morgan, DM 612, University College Library, Bristol], cited and described in Richards, R.J. (1987), p. 380. [Back to text]

36. Costall (1993). pp. 119-120. [Back to text]