Lessons for human science measurement from the quantification of earthquake size

Abstract

It remains controversial whether the human sciences can quantify the phenomena they study. The feasibility of quantification is usually assessed by identifying similarities and differences to quantitative measurement in physics. We argue that the case studies used to exemplify physical measurement are not sufficiently representative to underwrite such assessments. We substantiate this thesis by reconstructing how seismologists quantified “earthquake size.” Seismology demonstrates that quantification can succeed under conditions that, on the one hand, differ from canonical case studies and, on the other, resemble those of the human sciences in relevant respects—seismologists study phenomena that are not amenable to significant experimental control and that cannot be isolated from complex background conditions. This allows us to refute an influential argument for the impossibility of human science quantification, which turns on the claim that experimental control is a necessary condition for quantification (Trendler, 2009). Finally, we draw constructive lessons for the human sciences from the method that seismologists Charles Richter and Beno Gutenberg used to quantify earthquake size. That method starts by introducing (approximate and circumscribed) “placeholder” scales, which can then be extended and revised to account for inevitable disturbing factors in the measurement process. We use this method to identify promising developments but also continued shortcomings in a noteworthy effort at quantification: the Lexile measure of reading comprehension.