Aesthesiometric Compasses
maker, source: homemade
year made, acquired: c. 1900
box: l x w x h; 14 x 9 x 13 cm
markings on box and compasses: 26 through 50
The above compasses were part of a classroom excercise set for tactile threshold studies. Tactile compasses tested a person’s ability to discriminate two points from a single stimulus. Psycho-physicists mapped out the entire body to determine the difference thresholds at various locations. Lips were found to be the most sensitive area, while the back was the least sensitive.
Aesthesiometers can be traced back to the earliest psychophysical investigations. In the 1830’s, E. H. Weber’s used them in his tactile studies of perception. Weber coined the phrase "eben merklichen Unterschiede," or "Just Noticeable Difference."
The historian of Psychology, Rand Evans (1994), has described the more elaborate Aesthesiometers developed in the latter part of 19th century. Some of these devices had ivory tips to reduce temperature information, others had spring compression to ensure that investigators exerted an equitable amount of pressure on both points.
In the Literature:
Baldwin, James Mark (Ed.) (1902). Dictionary of Philosophy and Psychology. New York: MacMillan. pp. 611-612
Evans, Rand (1994). The Just Noticeable Difference: Psychophysical instrumentation and the determination of sensory thresholds, Proceedings of the Eleventh International Scientific Instrument Symposium, Bologna University, Italy, 9 - 14 September 1991. Dragoni, G. et al. (Eds.) Bologna: Grafis
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