JAMES McKEEN CATTELL AND THE METHOD OF CONSTANT STIMULI IN THE PSYCHOPHYSICS OF MOVEMENT

In 1892, Cattell & Fullerton published a paper on “The Psychophysics of Movement” in which they summarised their findings from the application of Fechner’s methods to the study of the extent, force, and time of arm movements made without the aid of vision. Using a form of Munsterberg’s apparatus (Titchener, 1905) they found the method of right and wrong cases to be ‘the most accurate of the methods’ and the difference associated with 75% correct judgement to be the ‘most convenient measure of discrimination’. By 1990s, however a major work on examining the role of proprioception in joint stability listed only the methods of adjustment (Joint Position Sense) and limits (Kinesthesia) as being ways of measuring movement sensitivity. Recent technical developments have enabled researchers to employ the Cattell & Fullerton method to obtain psychophysical measures of proprioception derived from the comparison of active movements made to physical stops. The first experiments on the psychophysics of active movement were conducted by Fechner (1860) with judgments of the amount of force required from the upper limb for it to overcome the resistance due to gravity for a specific weight. The judgments were then used to derive a measure of sensitivity. The experimental method employed by Peirce and Jastrow in 1884 involved judgment of the finger force needed to counter an upwards pressure on beam of a post-office scale from a weight placed in the pan, but it was not until the work of Fullerton & Cattell (1892) that the first judgments were made of differences in the extents of active movements made to physical stops. Methods of Constant Stimuli, Adjustment, and Limits in the Psychophysics of Movement The use of comparison of the extent of movements made to physical stops, without the aid of vision, as an experimental method for research into the psychophysics of movement seems to have been jointly developed by James McKeen Cattell and Hugo Munsterberg, who had been classmates in Wundt’s Psychophysical Seminar series in Leipzig in the summer of 1885 (Blumenthal, 1997). Munsterberg later supervised the dissertation of Edmund Burke Delabarre, presented in Freiburg in 1891, in which an apparatus he devised (Figure.1) for assessing both horizontal and vertical arm movements was used (Worringham, 1992). Edward Titchener (1905) lists his Fig. 30 as ‘Munsterberg’s apparatus’ and notes that the car, which travels on three horizontal tracks, has a vertically-set brass cylinder for the subject’s forefinger, and ‘two sliding blocks, which can be set at any point along the middle track, to mark the beginning and end of the two movements’ (p.104). In contrast, the apparatus used by Fullerton and Cattell (Figure 2) had a horizontal brass ring between the front and back wheels of the carriage, into which the seated subject