The Beginning and Growth of Measurement in Psychology

ASCIENCE has to undergo a good deal of development before it is ready to be founded, before it can be recognized as a distinct social institution with its separate books, journals, and appointments, as an independent enterprise to which some men devote their lives. A science, once founded, develops and changes, and sometimes the changes involve the addition of new fields to the old science, new fields that have histories of their own that were not part of the history of the science as it stood previously. In this way the history of psychology changes as psychology's present becomes enlarged, and it is not always clear just which events in the history of science belong to psychology. For instance, there are those who feel nowadays that psychology, as it moves over into the field of linguistics, should claim part of that history for its own, and there are others, but by no means as yet a majority, who think that psychology has now moved so far from physiology that it ought to give back some of its older history to the physiologists. Be those things as they may, there is, nevertheless, a pretty clear history of the entry of measurement into psychology and into those activities that eventually became psychology, and these events we find falling naturally into four fairly independent histories. (1) In the first place, there is the history of psychophysics, which may be thought of as founded in 1860 with the publication of Fechner's Elemente der Psychophysik, but which goes back nearly a hundred years more to the measurement of sensitivity and of the discriminatory capacity of the senses as accomplished by physiologists and other natural philosophers.l (2) Then there is the history of reaction time, which is at first the astronomer's learning to measure and take account of the personal equation in the observation of stellar transits, and then, when the discovery of galvanic electricity and electromagnets had made chronographs and chronoscopes available, the determination of actual individual differences in reaction times. First the physiologist Donders2 (1862) used these procedures to measure, as he thought, the times of various mental acts, and then the psychologists built an elaborate mental chronometry on these methods, generating an excitement about mental measurement that collapsed after thirty years.3 (3) There had been no quantitative measurement of learning or remember-