In pursuit of precision: The calibration of minds and machines in late nineteenth-century psychology

Benschop, R., & Draaisma, D. (2000). In pursuit of precision: The calibration of minds and machines in late nineteenth-century psychology. Annals Of Science, 57(1), 1–25.

The measurements have to be exact and observations as accurate as possible, instruments should register even small differences and yield outcomes on increasingly fine scales. Precision was developed for specific reasons and it was not linear shift but rather process that in each science it had its own course, pace, delays and stagnations. Psychological laboratory founded by Wundt (Leipzig, 1879) - the first of its kind in the world was the first place where actual cult of precision appeared, especially in the area of the measurement of reaction times to sensory stimuli. This experimental programme is also known as “mental chronometry” within which Wundt and his assistants set the standards of precision by means of an instruments and by using strict rules on the social organization of experiments. In this article origin and development of mental chronometry will be presented as well as Wundt’s effort to reach the degree of precision he considered necessary for the measurement of mental processes-one thousandth of a second.

Chronoscope- a clock-like instrument that was registering reactions in thousands of seconds was instrument every laboratory possessed. For classroom demonstrations chronoscope was often available as well as stopwatches and chronometers. All these chronometrical instruments were used to measure reaction times. The first to suspect that the velocity of the nerve impulse had a measurable speed was Helmholtz and his Dutch colleague F.C. Donders gave this research a psychological twist. Donders struggled from 1865 with a question whether the duration of processes such as distinguishing, willing and choosing can be measured. In experiment that marked the birth of “mental chronometry” an electrode was attached to the feet of an experimental subject. In one condition the subject knew in advance if a mild shock will be administered on the right or left foot and he had to move his hand as fast as possible on the side where he felt it thus breaking an electric switch. In the other condition the subject didn’t know on which foot the stimulus will be presented. Donder’s apparatus registered the difference in between these two conditions which was one-fifteenth of a second. It was the first time psychological process was able to determine and Donder’s registration of the reaction time marked the moment from which human mind was possible to measure. Donders did not continue with this research, it was taken over by Wundt and his assistants. Reaction time measurement turned psychology into a counting, a calculating, and a measuring science.

The instrument that contributed so much to the punctuality of psychological experimentation had its origins in the business of English artillery. In 1840 Charles Wheatstone constructed a device for measuring the velocity of projectiles. In 1842 there was an improved model of this instrument invented by the Swiss watchmaker and mechanic Mathias Hipp. The Hipp’s chronoscope had two dials where the hand of the upper dial turns once in one-tenth of a second and the hand on the lower dial makes one turn in ten seconds. The upper dial indicated milliseconds. It worked similar to the huge electric stopwatch. Even though it was technically advanced, the Hipp’s chronoscope was very sensitive to disturbances, and Wundt who was aware of tried to cope with it by constructing an instrument, which could serve as a standard for correction, called Control hammer. Still, there was a question is each calibration instrument needs its own calibration than how can one be sure if specific reading are true or actual time taken up by the psychological process under study? Wundt solved that problem by providing the Chronograph which had its origins in the astronomy where it was used for registering star transit. It was adjusted by Wundt so it was used for measuring extremely short intervals. Wundt’s experiments showed that the chronograph reduced the mean error in reaction-time experiments to 0.03 milliseconds. The mean error of the Hipp chronoscope was about ten times as large. Control hammer served to check other instruments and chronograph provided means for their calibration. Chronograph confirmed its special status by having the highest price of all the other available instruments, 1010 marks was double the price of chronoscope (440 marks).

Literature was important in promoting these instruments, where 3 texts were especially important in the Leipzig context: the Philosophische Studien (journal founded by Wundt in 1881); the Zimmermann catalogues of scientific apparatus and the Grundzüge der physiologischen Psychologie. The first article that appeared in the Philosophische Studien was “On Psychological Methods” and it was authored by Wundt who wrote that scientific psychology differs from usual psychology in the fact it strives to be precise.  In Philosophische Studien as well as in other journals were descriptions of psychological apparatus often supplemented by a footnote.

In Wundt’s book Grundzüge he described his vision of the new discipline of psychology and from second edition (1880) he also included separate paragraph about chronometric instruments and methods. Only experiments that were conducted with strict methodology were included in this book, where words such as precision, exactness, constancy, reliability, standardization were often used. Even though in the beginning Zimmermann’s catalogue was printed only in German, later began to appear in other languages as well. Wundt and his colleagues were not the only one preoccupied with precision; in the nineteenth century different genres of precision appeared in industry, government, science etc. In the mid-nineteenth century new branch of physics called metrology started to grow. It was a science dedicated to the creation and improvement of measuring methods, instruments and physical units and standards. In 1872 a group of scientists and industrialist among which were Wundt’s former teachers Hermann von Helmholtz and Emil Du Bois-Reymond issued a memorandum calling for state support in advancing precision-mechanism research. Werner von Siemens supported Schellbach Memorandum which led to the establishment of the world’s first institute devoted to the science and technology of precision measurement in 1887 called Physikalisch-Technische Reichanstalt. Even though experimental psychology may have shared with other disciplines the conventions and material methods of guaranteeing precision it did not share the object of the study. The purpose of manipulating instruments in psychology was to grasp the human mind.

In late 1883, James Mckeen Cattell, traveled to Leipzig to follow his field of experimental psychology. Wundt took him as a research assistant and Cattell was allowed to continue his research from America. Cattell’s work focused on the timing of recognizing and naming letters and words and their cognition. Cattell found the Hipp chronoscope to be too troublesome, it was yielding times that were too long. The problem could only be fixed by those whom understand electricity. Cattel had a battery of three La Clanche elements, which were supposed to emit constant stream, yet when tested, they kept fluctuating, this fluctuation he wanted to find in the people who operated the instruments: subjects and experimenter. Cattell wrote that both subjects seemed to remain determined and were not distracted from their attention by any outside source. He also wrote that if he spend six hours at work, two hours will be dedicated to preparing apparatus. In general he described his work as easy. At some point he also stated that days were passing so fast for him and each day looked like a previous one.

The culture of precision, constancy and regularity had reached every nook of the Leipzig laboratory and was soon spread to new laboratories in other countries. Distribution of experimental habits involved people, texts and instruments. Lot of students after they obtained their PhD would go back home and found their own laboratories which appeared everywhere as far as Tokyo. Twelve out of forty-three laboratories existing in America in 1900 were established by Wundt’s students. More than a third of the experimental instruments in the Harvard came from Leipzig. Other laboratories as well imported their machinery from Germany. Zimmermann catalogue was offering information about the apparatus and how to use them and was often referring to Grundzüge which was than referring to researches described in Philosophische Studien which would refer to catalogue thus creating a circle. Two years after he earned his PhD under Wundt, Edward Scripture-director of the Yale laboratory delivered a speech to the American Psychological Association in which pointed out the fact that psychologists in America make experiments without attending the most basic laws of scientific experimentation ( the Yale laboratory considered itself as part of tradition of precision). He also suggested that American psychologists should take example of Wundt and learn from his book, emphasizing that in Leipzig measurements are made with ever increasing accuracy and continual discovery of unexpected facts. He said America should be schooled in precision and in that process Leipzig should serve as a role model.  Wundt was aware of that and in Philosophische Studien he noted that his colleagues often approached him in order to find out how to get the apparatus he used and he would then refer them to his instrument-maker Krille.

In the introductory pages of “on the speed of mental processes” Donders reflected that physiology is a science of quantitative measurement and that phenomena of the human mind cannot be measured or evaluated. Surprisingly, he continued with idea that time opens up the human mind for measurement. Cattell described experimental physics as devoted to the measurement of time, space and mass in the material world while experimental psychology may measure time, complexity and intensity in consciousness.

Psychologists back in that time were insecure because of the unscientific heritage from philosophy that is why they were associate it with one of the established sciences such as physics, astronomy, physiology in order to share the prestige these sciences already earned. In the early 1890s, reaction time experiments in different laboratories, with apparently identical experimental arrangements produced very different results. Measuring them in milliseconds did not reduce these differences but emphasized them. Deviations in results were in some cases caused by individual differences between subjects or by other identifiable factors. Toward the mid-1890 it became clear that efforts to calibrate the experimental situation resulted differently than expected- each laboratory published a different result for the same psychological process even though accurate in millisecond.