Clark L. Hull was another important player in the operationalist movement in behavioristic psychology. He seemed more interested in the rpactice of science, in a manner comparable to that of the 19th century positivists, than arcane disputes about the nature of meaning. Despite being clearly influenced by Bridgman, he misinterpreted the significance of his work(Green, 1992).
In any case, by the important symposium of 1945, it was clear thatt there was little to no consensus on what the significance of operationalism was for psychology, or even really what it meant. The symposium was sponsored by the Psychological Review, and featured statements from Carroll Prayy, B.F. Skinner, Harold E. Israel, Percy Bridgman, Herbert Feigl and Edwin G. Boring. They were asked to respond to the following questions:
1. (a) What is the purpose of operational definitions? When are they called for?
(b) Logically, operational definitions could form an infinite regress. How is this regress limited in scientific practice?
2. When the same construct is defined by two different operations, should it be said that there are really two constructs?
3. (a) Are hypothetical operations which are physically impossible with present available techniques of scientific use?
(b) Is there a use for hypothetical operations that would define constructs which are presently non-existent (e.g. a color we cannot see)?
(c) Is there a use for hypothetical operations which could never be performed (e.g. the notion of infinity)?
4. Is experience a proper construct for operational definition?
5. Are there scientifically good and bad operations, and how are operations evaluated if they differ in value?
6. Is operationism more than a renewed and refined emphasis on the experimental method (as understood already by Galileo, if not Archimedes)?
7. Must operationists in psychology relegate theorizing of all sorts to the limbo of metaphysics?
8. What possible meaning is there in talking about improving or revising tests if there are no criteria outside the chosen test method?
9. Are all scientifically legitimate definitions operational in character?
10. What is a definition, operational or otherwise?
11. Can a phenomenon be identified or its properties be defined in terms of the events (operations) which are effective to produce, or occur as results of, the phenomenon? (Green, 1992)
There was much more disagreement than agreement on these questions. For example, Edward Boring, like the positivists, emphasized the importance of science being a public phenomenon, whereas Bridgman emphasized the importance of private experience. Indeed, it was because of this belief in the importance of private experience that he rejected behaviorism in general(Green, 1992).
Herbert Feigl, a faithful positivist, rejected the meaningfulness status of experience, and rejected talk about it as unscientific, and was joined in this by Pratt, whereas Boring and Bridgman accepted the possibility of operationalizing the concept. In any case, it is clear that, among those who describe themselves as operationists, there is a great deal of internal dispute, and agreement sometimes ends at the fact that each individual considered himself an operationist. Green (1992) points out that one of the most important tools operationism served for psychologist was the justification of intelligence testing in the 1920s.
Bridgman eventually repudiated the terms “operationism” and “operationalism.” The point he had been making in his original enunciation of the concept was far simpler than a full-blown philosophy which some had made it out to be(Green, 1992).
Sigmund Koch, a student of Feigl, who had initially been sympathetic to the operationist and behaviorist cause, would publish a withering attack on the doctrine in the early 1950s(Green, 1992). By the late 1950s, the vast majority of the most enthusiastic supporters of operationism had abandoned the cause. Even Bridgman himself eventually rejected it. Nevertheless, the concept of operational definitions remains important for psychologists. Indeed, the operational definition is regarded as an essential component of the coherent psychology experiment(Green, 1992).
Green, Christopher (1992). Of Immortal Mythological Beasts: Operationism in Psychology. Retrieved from: http://philsci-archive.pitt.edu/199/1/operat.htm. Theory & Psychology, 2, 291-320.