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The operational theory of measurement was developed in 1946 by Harvard psychologist Stanley Smith Stevens. Stevens' non-scientific theory of measurement is widely held as definitive in psychology and the behavioural sciences generally (Michell 1999).
It was partly developed to in response to the findings in the 1930s of the British Association for the Advancement of Science Ferguson Committee which had been setup to investigate the possibility of psychological attributes being measured scientifically. In its Final Report (Ferguson, et al., 1940), the Committee concluded that because psychological attributes were not capable of sustaining concatenation operations, such attributes could not be continuous quantities and therefore, they could not be measured scientifically.