Operationalization

Operationalization is the process of defining a concept as the operations that will measure the concept (variables) through specific observations.

That even the most basic concepts in science, like "length," are defined solely through the operations by which we measure them, is the discovery of Percy Williams Bridgman, whose methodological position is called operationalism. The fact we in practice measure "length" in different ways (it's impossible to use a measuring rod if we want to measure the distance to the Moon, for example) must mean that "length" logically isn't one concept but many. Each concept is defined by the measuring operations used.

Bridgman notes that in the theory of relativity we see how concepts like "length" and "duration" split into actually different concepts. It's painful for a physicist to realize that what she always thought was one concept is, in fact, two or more distinct concepts. However, if we only stick to operationally defined concepts, this will never happen again, Bridgman promises.

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 Equivalance 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. 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.