A behavioral economic analysis of fat appetite in rats.

A behavioral economic analysis of rats' consumption of various fat and sweet solutions was conducted in order to assess whether rats' fat appetite is readily modifiable. According to economic demand theory, changes in the price of a reinforcer will produce substantial changes in its consumption under conditions in which a substitutable reinforcer is available. Results from income-compensated price changes revealed that sucrose, mineral oil and saccharin solutions substituted for a corn oil solution: increases in the price of the corn oil led to large decreases in its consumption and sizable increases in consumption of these alternatives. On the other hand, plain water did not substitute for the corn oil solution: increasing the price of the corn oil did not result in nearly as marked a change in its consumption nor in consumption of the water. Neither the strength of preference for the corn oil under baseline conditions nor the caloric content of the alternative solution predicted whether the alternative reinforcer substituted for the corn oil. Rather, palatability appeared to be a dimension along which substitution was based. These results suggest that fat appetite is modified when palatable alternatives are available, independent of how strongly the fat is preferred.