Flavor avoidance learning based on missing calories but not on palatability reduction

Avoidance of a target flavor can be produced by providing rats with a highly nutritious solution of 20 % maltodextrin (20 %Malto) in some sessions and a 3 % maltodextrin (3 %Malto) solution containing the target flavor in intermixed sessions. Since 20 %Malto is both more nutritious and more palatable than 3 %Malto, flavor avoidance could arise because the flavor signals either a reduction in calories or reduced palatability, or both. Pilot testing established that rats strongly preferred 3 %Malto plus 0.1 % saccharin to both unflavored 3 %Malto and unflavored 20 %Malto. The two main experiments tested whether the palatability difference, which the pilot data had suggested was larger than the difference between 20 %Malto and 3 %Malto, could produce flavor avoidance. In both experiments, one group of rats were given 3 %Malto plus 0.1 % saccharin on some days, intermixed with other days on which this group was given 3 %Malto plus the target flavor, almond. Neither when trained and tested under conditions of food deprivation (Experiment 1) nor when trained and tested sated (Experiment 2) did palatability reduction produce almond avoidance. In contrast, calorie reduction produced almond avoidance under both conditions. These results suggest that flavor avoidance can be produced by intermixed training involving solutions that differ in nutritious value and palatability, but not when they differ only in palatability.