Experience-induced changes in sugar taste discrimination.

An apparent plasticity in glucose sensitivity was first noted while studying human taste variants, but the experimental design did not rule out regression to the mean. Since then, a human taste induction hypothesis that sensitivity for a taste stimulus increases with repeated exposure to it has been supported first by experience-induced changes in taste identification of monosodium glutamate and, subsequently, in sensory detection of glutaraldehyde, as well as in psychophysical and functional magnetic resonance imaging responses to novel taste stimuli. Yet, whether such plasticity occurs for the highly familiar taste of sugar remained unconfirmed. Therefore, we tested the taste induction hypothesis for sugar using a counterbalanced design, consisting of 3 pretreatment and 2 treatment conditions. The effects over time also were followed with an additional group of participants. The results showed that 1) experience with fructose significantly increases sensitivity for the taste of a sugar, glucose; 2) there are no significant differences in the sugar sensitivity between groups of randomly assigned participants before treatments; 3) a single session of 5 brief tastings of glucose has an effect on glucose sensitivity when tested 11 or 12 days later; and 4) without continued treatment, the increased sensitivity reverses within 33 or 34 days.