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. It states 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 the exercise of one which stands lower in the psychological scale. (Morgan, 1894, p. 53).
Morgan was reacting to excessively anthropomorphic interpretation of animal behavior, specifically the anecdotal approach of George Romanes. D.A. Dewsbury in Comparative Psychology in the Twentieth Century calls Morgan's Canon "[p]erhaps, the most quoted statement in the history of comparative psychology", which Frans de Waal echoes in The Ape and the Sushi Master : "perhaps the most quoted statement in all of psychology".
Morgan (1903, p. 59) later revised the Canon as follows:
- 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.
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.
- 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.
Interpretation of Morgan's Canon is not without controversy; see: