Sensory and metabolic feedback in the modulation of taste hedonics

One hundred and twenty-five college students were fed a small preload composed of common foods which were either solid or liquid, sweet or non-sweet, and high or low in energy content. At 15-minute intervals following the preload subjects rated the intensity and pleasantness of of either sweet or a non-sweet test stimulus. Pleasantness reductions (alliesthesia) were observed following all preloads but were significantly larger in the high-calorie groups. In addition, solid preloads were found to provoke greater hedonic shifts than liquid preloads. While intensity ratings paralleled those for pleasantness, no correlation between the two was apparent. The results point to a metabolic explanation for the hedonic declines in the test stimuli. Nutrient (perhaps carbohydrate) detectors in the upper GI tract are proposed to trigger both central and peripheral changes which underlie the changes in pleasantness and intensity judgements.