Bridgman notes that in the theory of relativity we see how concepts like "length" and "duration" split into actually different concepts. As part of the process of refining a physical theory, it may be found that what was one concept is, in fact, two or more distinct concepts. However, Bridgman proposes that if we only stick to operationally defined concepts, this will never happen.
The concept can perhaps be more clearly seen in the development of General Relativity. Einstein discerned that there were two operational definitions of "mass": accelerational, defined by applying a force and observing the acceleration, from Newton's Second Law of Motion; and gravitic, defined by putting the object on a scale or balance. Previously, people had not paid attention to the different operations used because they always produced the same results, but the key insight of Einstein was to posit the Principle of Equivalence that the two operations would always produce the same result because they were equivalent at a deep level, and work out the implications of that assumption, which is the General Theory of Relativity. Thus, a breakthrough in science was achieved by examining the operational definitions of scientific measurements.
To operationally define basic concepts has now become central to all sciences, not only to physics.
Operationalization is often used in the social sciences as part of the scientific method and psychometrics. For example, a researcher may wish to measure "anger." Its presence, and the depth of the emotion, cannot be directly measured by an outside observer because anger is intangible. Rather, other measures are used by outside observers, such as facial expression, choice of vocabulary, loudness and tone of voice.
If a researcher wants to measure the depth of "anger" in various persons, the most direct operation would be to ask them a question, such as "are you angry", or "how angry are you?". This operation is problematic, however, because it depends upon the definition of the individual. One person might be subjected to a mild annoyance, and become slightly angry, but describe themselves as "extremely angry," whereas another might be subjected to a severe provocation, and become very angry, but describe themselves as "slightly angry." In addition, in many circumstances it is impractical to ask subjects whether they are angry.
Since one of the measures of anger is loudness, the researcher can operationalize the concept of anger by measuring how loudly the subject speaks compared to their normal tone. However, this must assume that loudness is uniform measure. Some might respond verbally while other might respond physically. This makes anger a non operational variable.
One of the main critics of operationalism in social science argue that "the original goal was to eliminate the subjective mentalistic concepts that had dominated earlier psychological theory and to replace them with a more operationally meaningful account of human behavior. But, as in economics, the supporters ultimately ended up "turning operationalism inside out" (Green 2001, 49). "Instead of replacing 'metaphysical' terms such as 'desire' and 'purpose'" they "used it to legitimize them by giving them operational definitions." Thus in psychology, as in economics, the initial, quite radical operationalist ideas eventually came to serve as little more than a "reassurance fetish" (Koch 1992, 275) for mainstream methodological practice."
The above discussion links operationalization to measurement of concepts. Many brilliant scholars have worked to operationalize concepts like job satisfaction, prejudice, anger etc. Scale and index construction are forms of operationalization.
Operationalizaton is part of the empirical research process. Take for example an empirical research question: Does job satisfaction influence job turnover? Both job satisfaction and job turnover need to be measured. The concepts and their relationship are important - operationalization occurs within a larger framework of concepts. When there is a large empirical research question or purpose the conceptual framework that organizes the response to the question must be operationalized before the data collection can begin. If a scholar constructs a questionnaire based on a conceptual framework, they have operationalized the framework. Most serious empirical research should involve operationalization that is transparent and linked to a conceptual framework.
To use an oversimplified example, the hypothesis Job Satisfaction reduces job turnover is one way to connect (or frame) two concepts - job satisfaction and job turnover. The process of moving from the idea job satisfaction to the set of questionnaire items that form a job satisfaction scale is operationalization. For most of us, operationalization outside the larger issue of a research question and conceptual framework is just not very interesting.
In the field of Public Administration Shields and Tajalli (2006) have identified five kinds of conceptual frameworks (Working Hypotheses, descriptive categories. practical ideal type. operations research and formal hypotheses). They explain and illustrate how each of these frameworks can be operationalized. They also show how to make conceptualization and operationalization more concrete by demonstrating how to form conceptual framework tables that are tied to the literature and tables that lay out the specifics of how to operationalize the conceptual framework.
To see examples of research projects that use these tables see http://ecommons.txstate.edu/arp/
Shields, Patricia and Hassan Tajalli. 2006. Intermediate Theory: The Missing Link to successful Student Scholarship. Journal of Public Affairs Education. Vol. 12, No. 3: 313-334. http://ecommons.txstate.edu/polsfacp/39/