In the lab with George: 20 years without plumbing or wiring

George Collier has shown us the importance of non-physiological, economic factors in the control of food intake. Several studies are reviewed demonstrating the effects of cost on rats' diet selection when offered sweet solutions and rat chow. When sucrose solution and chow are both available at no cost, rats take upto 70% of their daily calories from sucrose depending on the concentration. However, when they must pay for sips of sucrose solution, sucrose intake falls as sip price increases. Because in take of free chow increases as costly sucrose intake declines, total daily calorie intake is constant. If the rats must bar press for both chow and sucrose solution, the intake of each commodity depends on its own cost as well as the cost of the alternative commodity. As the intake of one commodity falls with its price, intake of the other commodity increases. However, rats are less willing to give up costly chow than costly sucrose, indicating that sucrose is an incomplete substitute for chow despite its sweet taste. However, if saccharin is available at no cost, rats that must bar press for chow pellets increase their saccharin intake as their chow intake falls with chow cost. This change in saccharin intake is not seen when saccharin is costly. These results suggest that although the postingestive properties and, to a lesser extent, the taste, of a commodity influence its inclusion in a rat's diet, robust changes in intake and diet selection also occur in response to the cost of the foods, a factor that does not affect either taste or postingestive consequences.