Operational Definition, Legacy of Positivism

Lecture 18.  October 23 and 27.

Afterthoughts.  Positivists such as Comte believed that the basis of all truth-claims was direct observation of nature — positive knowledge.  We have seen that this caused a problem for science later in the 19th century when physicists and chemists started talking about things such as atoms and sub-atomic particles, and physicists such as Mach opposed their acceptance into science on positivist grounds.  They thought that all speculative beliefs, whether about God or angels or demons or even atoms, should be shunned as unverifiable and unscientific.  However, Mach and the strict positivists lost that debate.

Forethoughts.  But positivism adapted.  In the early 20th century a new form of positivism, Logical Positivism, arose in Vienna, along with psychoanalysis, the Bauhaus movement and other ideological fruits of modernity, and it dominated philosophy of science for 75 years.  Logical Positivism reconciled traditional positivism’s grounding of knowledge in observation with scientific use of terms referring to unobservable entities with a concept psychologists know as operational definition.  According to LP, a concept that seems to refer to something unobservable is legitimate in science if and only if the concept can be linked to something observable, typically a measurement or procedure of some kind, hence the phrase operational definition.  The term is defined by a scientific operation that can be observed.  Thus, for example, “mass” is a property of objects that cannot be seen, but can be operationally defined as weighing an object at sea level.  Or “electron” might be defined as a characteristic tracing on a photograph from a particle collider. 

Notice that there is a clever move here.  I wrote above about concepts that “seem to refer” to something observable.  Most scientists and ordinary people would think that “electron” refers to a particle too small to be seen, but LP denies this, because it, like traditional positivism, wants to exclude unobservable entities from science as dangerously metaphysical or religious.  According to LP, the meaning of a scientific term is exhausted by its operational definition — theoretical terms don’t refer to anything at all beyond the operation used to define them.

Operational definition was introduced to psychology in the 1930s by the psychophysicist S. S. Stevens, and it had an enormous influence on the field, an influence still felt today anytime a psychologist “operationalizes” a concept.  Operationism gave a huge boost to the redefining of psychology as the science of behavior rather than as the science of the mind.  Because consciousness is private, it cannot be observed by the scientific community, and cannot, therefore, produce positive knowledge.  However, behavior can be observed, and theoretical terms that allegedly refer to mind such as “drive,” “habit,” or “cognitive map,” could be redefined operationally as “hours of food deprivation.” “number of reinforced responses,” or “locating the food in a maze.”   Perhaps the most famous operational definition in psychology was given by E. G. Boring: “Intelligence is what the tests test.”  It’s important to note that according to LP there is no such thing as (or need be no such thing as) drive, habit, cognitive map, or intelligence, there are just the operational definitions of the terms.  Legitimating theoretical terms in science was, for LP, just a language trick.

However, despite psychologists continued devotion to operational definition, there’s really no such thing.  If you are interested in more on this topic, see Green, C. D. (1992).  Of Immortal Mythological Beasts: Operationism in Psychology.  Theory and Psychology, 2, 291-320.  Available at http://www.yorku.ca/christo.  Click on “Research and CV” tab, and then choose the highlighted title of the article.


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