Learned flavor preferences. The variable potency of post-oral nutrient reinforcers

The notion that preferences for flavors paired with various nutrients can be attributed simply to their energy content (flavor-calorie learning) is belied by variation in nutrient reinforcing potency. Fructose, fat and ethanol, all regarded as powerful contributors to food and fluid preferences, are less potent than glucose when their orosensory effects are bypassed. Conditioning studies in animals infused with nutrients as they consume target flavor solutions have shown that the weaker reinforcing effects of these nutrients can be enhanced by various methods that improve the opportunity for associating a flavor with post-oral effects. Until the nature of the reinforcing stimuli is understood, flavor-nutrient learning is a better label for these phenomena. (C) 2008 Elsevier Ltd. All rights reserved.