ABSTRACT
From the time when the earliest predecessors of experimental psychology began collecting quantitative observations of behavior, mathematical methods have been drawn on to aid in ordering and interpreting data. Measurements of the accuracy with which observers could detect simultaneous occurrences of events in astronomical observatories and determinations of sensory thresholds—that is, the intensities of stimuli just capable of evoking responses—in physiological experiments could be accomplished using only simple methods long familiar in physical science. However, these measurements were only the first steps toward a new discipline of psychophysics, or, more broadly, experimental psychology, with the new goal of generating quantitative representations of psychological attributes such as sensations, action tendencies, or values that could be inferred from observations. Moving toward this goal required a new theoretical apparatus that has come to be known as psychological measurement, or scaling, theory, and means of dealing with problems of reliability of measurements, met by the importation of statistical methods and theory developed in physical and biological sciences.
