Gustatory processing differences in PTC tasters and non-tasters: a reaction time analysis.
The present study examined differences in gustatory processing for tasters and non-tasters of phenylthiocarbamide (PTC) by assessing intensity judgment reaction times in these two groups. After prescreening for sensitivity to PTC, subjects were asked to judge whether solutions of sucrose, sodium chloride, quinine sulfate, hydrochloric acid and PTC were weak, medium or strong as quickly as they were able. Based on the reaction time and PTC sensitivity data, three groups of subjects were identified; tasters, sensitive non-tasters and less sensitive non-tasters. The taster population was characterized by their high sensitivity to PTC and a typical, negatively skewed distribution of reaction times. Sensitive non-tasters demonstrated a distribution of reaction times that was similar to that observed with tasters. However, these subjects were insensitive to PTC. The less sensitive non-tasters were insensitive to PTC and produced reaction times that were significantly slower than those produced for the other two groups across all of the substances tested. It is hypothesized that two groups of PTC non-tasters exist. One group has a specific deficit involving PTC and related compounds. The other group demonstrates sensitivity deficits for a wide range of gustatory stimuli.