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Coined by 19th-century British psychologist C. Lloyd Morgan, Morgan's Canon (more usually called Lloyd Morgan's Canon, or occasionally Morgan's Canon of Interpretation) remains a fundamental precept of comparative (animal) psychology. In its developed form it states that:

In no case is an animal activity to be interpreted in terms of higher psychological processes, if it can be fairly interpreted in terms of processes which stand lower in the scale of psychological evolution and development. (Morgan 1903, p. 59)

In other words we should only consider behaviour as, for example, rational, purposive or affectionate if there is no other explanation in terms of the behaviours of more primitive life-forms to which we do not attribute those faculties.


Morgan was reacting to excessively anthropomorphic interpretation of animal behavior, specifically the anecdotal approach of George Romanes. The prestige of Lloyd Morgan's canon partly derives from the fact that Lloyd Morgan was himself an acute observer of behaviour, and provided convincing examples of cases where behaviour that apparently involved higher mental processes could in fact be explained by simple trial and error learning (what we would now call operant conditioning). A famous example is the skilful way in which his terrier Tony opened the garden gate, easily taken by someone seeing the final behaviour as an insightful act; Lloyd Morgan, however, had watched and recorded the series of approximations by which the dog had gradually learned the response, and could demonstrate that no insight was required to explain it.


As the study of animal cognition has become popular, a disciplined use of Lloyd Morgan's canon has become more and more important. D.A. Dewsbury calls Morgan's Canon "perhaps, the most quoted statement in the history of comparative psychology"[1] and Frans de Waal echoes in The Ape and the Sushi Master : "perhaps the most quoted statement in all of psychology". It has played a critical role in the growth of the prestige of behaviourism in twentieth century academic psychology.

Lloyd Morgan's Canon is usually thought of as a special case of Occam's razor by virtue of its presupposition of simplicity that lower level interpretations are more parsimonious than higher level ones. See also the use of Morgan's canon in Biology at Occam's Razor.

References Edit

  1. D.A. Dewsbury, Comparative Psychology in the Twentieth Century


  • Morgan, C. L. (1894). An introduction to comparative psychology. London: W. Scott.
  • Morgan, C. L. (1903). An introduction to comparative psychology, 2nd edition. London: W. Scott.
  • Epstein, R. (1984). The principle of parsimony and some applications in psychology. Journal of Mind and Behavior, 5, 119-130.
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