Abstract

With S.S. Stevens, operationism became an important influence in psychology. In this paper I discuss the differences between Bridgman's and Stevens' proposals on operationism and the role that operational definitions play in scientific theory. I discuss how Stevens' notions of the basic act of discrimination and of the relation procedure–outcome influenced B.F. Skinner's criteria under which the main conceptual distinctions in operant psychology were formulated. The operational origin of the dichotomies between respondent and operant behavior, contingency-shaped and rulegoverned behavior, private and public events, and verbal and nonverbal behavior are examined.