S.S. Stevens, operationalism, and logical positivism

Nabeel Hamid

University of Pennsylvania

This paper argues for two related theses. First, I submit that the arrival of logical positivism in North America in the mid-1930s influenced the development of operationalism in psychology, as evidenced in a series of papers by S.S. Stevens from 1935 to 1939. Stevens in this period takes up three key logical positivist ideas: the distinction between formal and empirical statements, Carnap's distinction between the material and formal modes of speech, and a broadly Russellian conception of class formation. I thus push back on recent scholarship (esp. Feest 2005) that challenges a long-standing criticism of operationism (e.g. Leahey 1981; Green 1992). According to the view that Feest questions, operationalists such as S.S. Stevens had accepted (largely uncritically) logical positivist doctrines of the verificationist principle, and the analytic/synthetic distinction and, consequently, the demise of these philosophical theses in the course of internal refinements (e.g. Carnap 1936; Hempel 1950) and external critique (e.g. Quine 1953) proved just as damaging for operationalism. Feest rejects the historical assumption, implicit in such criticisms, of shared origins of logical positivism and operationalism. While I accept her claim that logical positivism and operationalism originated independently, I nonetheless argue that the arrival of Vienna Circle figures in American academia influenced considerably its subsequent development, in ways that survived the decline of logical positivism. Second, I show that Stevens, by assimilating logical positivist notions, was able to develop an original solution to the "problem of generality" – the charge that operationalism, by defining each concept in terms of a particular set of concrete operations, fails to provide for the generalization of concepts. According to Stevens, generalization in operationalist psychology begins by collecting as members of a class all the observable, discriminated responses to variations in stimuli that satisfy certain operational criteria, and then assigning a name or symbol to that class. Classes of classes are formed on the basis of relations identified among the elementary classes. The problem that confronts Stevens here is that the relations among classes of classes do not correspond to any operational procedures, hence appear not to be grounded in empirical criteria. His solution is to treat this second level of generalization as akin to the formation of hypotheses. Stevens regards hypotheses as a species of formal statements, insofar as hypotheses are arrays of symbols ordered only by syntactic rules of coherence, and lack denotation. But hypotheses differ from the statements of logic and mathematics in that the symbols in hypotheses could acquire denotation, hence potentially become operationalized, through subsequent observations. Hypotheses, for Stevens, constitute a distinct class of formal statements to the extent that their initial formulation is constrained not only by the coherence of their symbols, but also by a space of operational possibilities in a future state of research. Stevens' thinking in this matter, I argue, reveals a rich synthesis of methodological concerns in psychology with conceptual tools offered by logical positivism.