Citation of Laws and Theories in Textbooks across 112 Years of Psychology

Data concerning citation of laws ( n = 157) and theories ( n = 699) were collected from psychology textbooks across 112 years (1885–1996) of psychology. Three hypotheses concerning the comparative “citation strength” of the terms law and theory in psychology were set up to be tested: (1) the number of laws cited in psychology textbooks has increased over 112 years; (2) the number of theories cited in psychology textbooks has increased over 112 years; and (3) the ratio of laws-to-theories cited in psychology textbooks has remained relatively balanced over 112 years. Results showed that Hypotheses 1 and 3 were not confirmed, and Hypothesis 2 was confirmed. It was suggested that psychology has a need for a more balanced relationship between number of laws and theories cited in textbooks. Supplemental analyses tracked citation counts of specific laws and theories across 112 years to detect strength of citation and change in those concepts over time. Research was suggested concerning the semantic issues associated with use of the terms law and theory in psychology.