Mouth-state dependent changes in the judged pleasantness of water at different temperatures

Dehydration increases the pleasantness of cold (0 degrees C) water (Boulze et al., 1983, Physiol. Behav. 30:97-102, 1983). The hypothesis that the mouth dryness induced by dehydration mediates this hedonic shift was investigated. Hydrated assessors (n = 16) judged 3 degrees C water as more pleasant after artificial mouth drying than did controls (n = 16). Mouth drying failed to influence similar judgements of water 13 degrees C, 23 degrees C, and 33 degrees C. We propose that preference shifts depend on temperature because cold water offers more rewarding relief from the sensations resulting from mouth dryness. Measures on saliva production were consistent with this proposal. Assessors swilled with water (3 degrees C, 13 degrees C, 23 degrees C, and 33 degrees C) for 5 a and then emptied their mouths. Measures of subsequent saliva flow confirmed that cold (3 degrees C) water induces an:elevated rate of saliva flow and consequently leaves the mouth in a wetter state. (C) 1997 Elsevier Science Inc.