The Interstimulus Interval for Taste: 1. The Efficiency of Expectoration and Mouthrinsing in Clearing the Mouth of Salt Residuals

Abstract

Various interstimulus procedures ranging from rapid expectoration to up to 50 tapwater mouthrinses were examined in relation to how efficiently they cleared the mouth of residuals from a mouthrinse with equimolar 1 M NaCl and LiCl. Samples of expectorated saliva were analysed for Na and Li by flame photometry, the Li being used as a tracer for exogenous Na. It was found that exogenous salt residuals were not cleared from the mouth after 30 min rapid expectoration nor by fewer than 20 mouthrinses. On the other hand, ‘suprathreshold’ concentrations were cleared by ∼10 min rapid expectoration or 5 mouthrinses. Such rigorous interstimulus procedures are not generally used in taste experiments with stimuli of comparable concentration. Tapwater rinses were also seen to leave their own residuals in the mouth while the ad-lib rinsing procedure was found to be not only uncontrolled but also ineffective.