Operational definition

An operational definition specifies concrete, replicable procedures designed to represent a construct. In the words of American psychologist S.S. Stevens (1935), "An operation is the performance which we execute in order to make known a concept."^[1]^[2] For example, an operational definition of "fear" (the construct) often includes measurable physiologic responses that occur in response to a perceived threat. Thus, "fear" might be operationally defined as specified changes in heart rate, galvanic skin response, pupil dilation, and blood pressure.^[3]

^ Stevens, S. S. (1935). The operational basis of psychology. American Journal of Psychology, 47 (2): 323–324, 330. doi:10.2307/1415841. "We must first define an operation; and, if we are to be consistent, we must define it operationally. An operation is the performance which we execute in order to make known a concept. ... [Discrimination] is the sine qua non of any and every operation including that of denoting. In this sense discrimination is the fundamental operation of all science. ... We must define the criteria by which we determine the applicability of a term in a given instance and then ... maintain constant vigil against the human tendency to read into a concept more than is contained in the operations by which it is determined." (emphasis in original).
^ Ribes-Iñesta, Emilio (2003). What is defined in operational definitions? The case of operant psychology. Behavior and Philosophy, 31: 115. "Operational definitions consist of the specification of procedures and expected outcomes (procedures used for producing and measuring a phenomenon) as the necessary criteria for establishing that the terms defined are empirically meaningful."
^ Lang, P. J.; Davis, M.; Ohman, A. (2000). "Fear and anxiety: animal models and human cognitive psychophysiology". Journal of Affective Disorders. 61 (3): 139. doi:10.1016/s0165-0327(00)00343-8. ISSN 0165-0327. PMID 11163418. Electrical stimulation of the amygdala elicits many of the behaviors used to define a state of fear, with selected target areas of the amygdala producing specific effects (Fig. 1).

[1] Stevens, S. S. (1935). The operational basis of psychology. American Journal of Psychology, 47 (2): 323–324, 330. doi:10.2307/1415841. "We must first define an operation; and, if we are to be consistent, we must define it operationally. An operation is the performance which we execute in order to make known a concept. ... [Discrimination] is the sine qua non of any and every operation including that of denoting. In this sense discrimination is the fundamental operation of all science. ... We must define the criteria by which we determine the applicability of a term in a given instance and then ... maintain constant vigil against the human tendency to read into a concept more than is contained in the operations by which it is determined." (emphasis in original).

[2] Ribes-Iñesta, Emilio (2003). What is defined in operational definitions? The case of operant psychology. Behavior and Philosophy, 31: 115. "Operational definitions consist of the specification of procedures and expected outcomes (procedures used for producing and measuring a phenomenon) as the necessary criteria for establishing that the terms defined are empirically meaningful."

[3] Lang, P. J.; Davis, M.; Ohman, A. (2000). "Fear and anxiety: animal models and human cognitive psychophysiology". Journal of Affective Disorders. 61 (3): 139. doi:10.1016/s0165-0327(00)00343-8. ISSN 0165-0327. PMID 11163418. Electrical stimulation of the amygdala elicits many of the behaviors used to define a state of fear, with selected target areas of the amygdala producing specific effects (Fig. 1).

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