Parsimony in Psychology

Psychology has as yet produced relatively few facts or principles of sufficient reliability and consistency to be dignified by the term "law," and virrually none which have proved to be lresistant to continual modification in the light of newly acquired knowledge. In fact, there are perhaps fewer consistencies of this order in the typical behavioral subject matter of psychology than can be found in the behavior of the psychologist himself as scientific investigator, of which no better illustration exists than his acceptance of the age-old "law of parsimony." Assumptions concerning th: fundamental simplicity of the universe and consequent appeal to economy acd simpliciry in the explanatory efforts of science can be traced back as far as the philosophic origins of the scientific method. However, the formulation of the law or principle of parsimony is generally credited to William of Occam, whose "entities should not be multiplied beyond necessity" is also known as Occam's Razor. Despite the widespread acceptance of the law of parsimony as a fundamental tenet of scientific method, its usage in psychology has been characterized by considerable confusion and imprecision. This is in large measure due to its historically close association with Lloyd Morgan's Canon rejecting anthropomorphism and "higher psychical faculties" in the explanation of animal behavior (Morgan, 1894). As a result, many psychologists have equated Occam's Razor with Morgan's Canon, in spite of efforts to distinguish clearly berween them (e.g., Adams, 1928; Newbury, 1954). Confusion has also reigned as to h e proper range of application of the law of parsimony within psychology. Initially,