TASTE STIMULATION AND PREFERENCE BEHAVIOR 



263 



expected that not only thresholds for saline but thresholds for many other 

 stimuli might be similarly dependent upon salivary composition. Indeed, 

 Cragg (1937) a number of years ago showed that salivary pH was related to 

 threshold for acids. Our observations extend this concept to salt sensitivity 

 and further suggest that a simple process of adaptation may account for the 

 effect. 



H2O .069 .69 



Adapting Solution (mM NaCI) 



15 



Fig. 4. The relation between adapting solution on the tongue and threshold. 

 Each point shows the threshold obtained on one experimental determination ; solid 

 dots for adaptation to water or salt, open circles where the tongue is adopted 

 to saliva with a Na^- composition shown on the abscissa as determined by flame 



photometry. 



It should be noted that when adapted to the salts used in our studies, S's 

 reported no salty sensations at all, even for the strongest stimulus. Yet, 

 when adapted to water, these same stimuh elicited strong sensations of 

 saltiness. At the end of the experiment, the change in taste due to adapta- 

 tion was demonstrated to each S. Each was genuinely surprised at the 

 effect. 



The magnitude of the changes in sensitivity induced by adaptation lie 

 clearly within the order of changes reported by Yensen and others when 



