Food reward. What it is and how to measure it.

We investigated the contribution of hunger and food liking to food reward, and the relationship between food reward and food intake. We defined liking as the pleasantness of taste of food in the mouth, and food reward as the momentary value of a food to the individual at the time of ingestion. Liking and food reward were measured, respectively, by ratings of the pleasantness of the taste of a mouthful, and ratings of desire to eat a portion, of the food in question. Hunger, which we view as primarily the absence of fullness, was rated without food being present. Study 1 provided evidence that hunger and liking contribute independently to food reward, with little effect of hunger on liking. Food intake reduced liking and reward value more for the eaten food than uneaten foods. The results were ambiguous as to whether this food-specific decline in reward value ('sensory-specific satiety') involved a decrease in 'wanting' in addition to the decrease in liking. Studies 2 and 3 compared desire to eat ratings with work-for-food and pay-for-food measures of food reward, and found desire to eat to be equal or superior in respect of effects of hunger and liking, and superior in predicting ad libitum food intake. A further general observation was that in making ratings of food liking participants may confuse the pleasantness of the taste of food with the pleasantness of eating it. The latter, which some call 'palatability,' decreases more with eating because it is significantly affected by hunger/fullness. Together, our results demonstrate the validity of ratings of desire to eat a portion of a tasted food as a measure of food reward and as a predictor of food intake.