Ratio Scaling, Taste Genetics, and Taste Pathologies
Linda M. Bartoshuk Yale University
In the early 1960s Don McBurney and I were working on related projects in Carl Pfaffmann's laboratory at Brown University. McBurney was using classic threshold methods to study the effects of adaptation on taste in human subjects, and I was just beginning to record neural responses to water in the chorda tympani nerves of cats. McBurney and Pfaffmann ( 1963) showed that adaptation to NaCl (including the NaCl in saliva) causes the NaCl threshold to rise to a point just above the adapting solution. This made us wonder what happened to the NaCl concentrations below threshold. Did they become tasteless? My first paper was our investigation of this ( Bartoshuk, McBurney, & Pfaffmann, 1964). We adapted tongues to NaCl and then asked subjects to describe the qualities of concentrations above and below the adapting concentration. We found that concentrations lower than the adaptation concentration tended to be called bitter or sour, whereas those above were either sweet or salty. The bitter-sour sensations produced by the subadapting concentrations were called water tastes.
The apparatus we used was that designed by McBurney for his threshold work. The subject sat in front of a water bath holding the stimuli, extended his or her tongue, and the adaptation solution was flowed across the extended tongue. The first water bath consisted of a big galvanized tub (about 4 feet long) with a thermal sensing unit that heated copper tubing when the temperature of the bath went below 34°C (the temperature of the