Taste judgements and gustatory stimulus duration: taste quality, taste intensity, and reaction time

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Abstract
Human taste quality and intensity judgements and vocal complex taste reaction times to liquids flowing across 39.3 mm2 of the anterodorsal tongue were measured for stimulus durations of 50, 100, 300, 1000 and 2000 ms. No restrictions were placed on the descriptions that subjects might use for identifying a stimulus liquid. Quality reaction times were at least 200 ms longer than previously measured vocal simple taste reaction times. Median vocal taste quality reaction times ranged from 754 to 1050 ms for 500 mM NaCl, 2 mM sodium saccharin in 10 mM citric acid (artificial lemonade), 214 mM monosodium glutamate (MSG) and 2 mM sodium saccharin (NaSac). Duration had little effect on quality or quality reaction time. For some stimuli, few descriptors were used: descriptions of NaSac used only three terms across all subjects and stimulus durations; of NaCl, five. The word ‘sweet’ was ≥90% of all NaSac verbatim descriptions; the word ‘salty’, ≥90% of all NaCl descriptions, the word ‘sour’ or the word ‘sweet’, ≥60% of all artificial lemonade descriptions, at all durations. For other solutions, including 250 and 500 mM MgSO4, and 3.2 and 10 mM HC1, six or more descriptive terms were required. In all cases, ≥90% of descriptors were ‘sour’, ‘bitter’, ‘salty’ or ‘sweet’, or adjective compounds of them. Judged intensity consistently increased with stimulus duration from 50 ms through 2000 ms, more than doubling between 50 and 1000 ms. Intensity reaction times exceeded 1400 ms at all durations, with a 1467–2006 ms range.